On the Occurrence of the ' Enteronephric'
Type of Nephridial System in Earthworms of
the Genus Lampito.
By
Karm Narayan Bahl, D.Sc, D.Phil.,
Professor of Zoology, Lucknow University, India.
With Plate 2 and 2 Text-figures.
CONTENTS.
PAGE
1. I N T R O D U C T O R Y
.
2.
HISTORY
3.
T H E NEPHRIDIAL
(a)
(6)
(c)
(d)
(e)
.
.
.
O PO U R K N O W L E D G E
SYSTEM
.
.
.
O F T H E GENUS
.
07
L A M P I T O .
O FL A M P I T O
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.
.
T h e G e n e r a l P l a n oft h e S y s t e m
.
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T h eEnteronephric Meganephridia .
.
.
T h eD u c t s a n d Openings oft h e Meganephridia .
The Exonephric (Integumentary) Micronephridia
The Pharyngeal Nephridia and their Ducts
.
OP THE NEPHRIDIA
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73
81
84
S5
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4.
T H EBLOOD-SUPPLY
5.
DISCUSSION
6.
MATERIAL
7.
SUMMARY
8.
REFERENCES TO LITERATURE .
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97
EXPLANATION
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98
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AND TECHNIQUE
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OP PLATE
1.
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IN L A M P I T O
70
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87
88
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INTRODUCTORY.
EVER since I discovered the ' enteronephric' type of
nephridial system in the perichaetous earthworm P h e r e tima (1), I have been on the look-out for other earthworms
which would show the same type of nephridial system, since
there was no reason to suppose that this characteristic type
of excretory system is confined to a single genus amongst the
F 2
68
HARM NARAYAN BAHL
Oligochaeta. If, as I believe, the purpose of this type of
excretory system is to conserve water during periods of
drought, we should expect to find a similar provision made for
economy of water in some at least of the other tropical earthworms. I naturally thought that the best forms to examine
for this purpose would be those belonging to the allied genera
Megascolex and L a m p i t o . Last February (1922), while
on a visit to Madras, I obtained, through the courtesy of
Professor K. Eamuni Menon, of the Presidency College, a few
specimens of earthworms belonging to the genus L a m p i t o ,
and on examining these worms I was agreeably surprised to
find that their nephridial system was ' enteronephric '. While
I had the work on Madras L a m p i t o in hand, Miss M. L.
Hett of Delhi sent me a few specimens of earthworms asking
me what they were. Luckily they also turned out to be
L a m p i t o . Later, in May and June of the same year (1922),
while •working at the Ceylon University College, I found and
collected a large number of specimens of L a m p i t o at
Colombo which I was able to fix and preserve myself. Most of
the work embodied in this paper has been done on the Colombo
specimens, and I have to thank Mr. E. Mam of the Ceylon
University College for the facilities he provided for my work
at Colombo. I am also very grateful to Miss Hett and Professor
Eamuni Menon for kindly sending me, at my request, specially
fixed and preserved specimens of Lampito from Delhi and
Madras respectively.
As I shall discuss in the next section of this paper, the
genus L a m p i t o has sometimes been recognized as a separate
genus and at others been included in the larger genus Megascolex. Its nephridial system has already attracted the
attention of various observers because of its peculiar formation,
consisting of micronephridia throughout the body and meganephridia in addition in the post-clitellar segments. In fact,
it was the possession of this peculiar form of nephridial system
that led Michaelsen (9) to constitute the separate genus
L a m p i t o . This peculiarity has now been shown to exist
in several other genera of the sub-family Megascolecinae,
ENTERONEPHRIC NEPHRIDIAL SYSTEM IN EARTHWORMS
69
e.g. Megascolides, Notoscolex, Megascolex, and
P l e i o n o g a s t e r . The present investigation dealing only
with the nephridia of Lampito carries this peculiarity still
further, and shows that the meganephridia of the post-clitellar
segments of this worm are enteronephric. They are not
comparable to the meganephridia of Lumbricus or Allolobophora, but to the septal nephridia (micronephridia)
of P h e r e t i m a . They do not open to the exterior but into
the lumen of the gut at segmental intervals.
As a result of this investigation, the terms relating to the
nephridia of earthworms would seem to need revision. I have
already shown (1) that the term ' plectonephric ' implying
a network is inapplicable to the nephridia of P h e r e t i m a ,
since there is no network in this worm, and it is doubtful
whether a network of nephridia exists in any earthworm at all.
The term ' plectonephric ' originally introduced by Benham
is thus rendered obsolete and has already fallen into disuse,
and the terms noAV in use are ' m i c r o n e p h r i d i a ' and
' m e g a n e p h r i d i a ' . In P h e r e t i m a , which is a micronephridial genus, we have recognized two types of nephridia,
namely the ' exonephric ' and the ' enteronephric ', according
as they open to the exterior or into the gut (1). We shall now
have to extend this distinction and recognize two types of
meganephridia also, namely the ' exonephric 'or Lumbricus
t y p e of meganephridia which open to the exterior, and the
' enteronephric 'or Lampito t y p e of meganephridia which
open into the gut at each intersegmentum.
We are thus able to recognize four kinds of nephridia amongst
earthworms, namely the exonephric micronephridia (e.g.
integumentary nephridia of P h e r e t i m a and Megascolex) and the exonephric meganephridia (e.g. ordinary
nephridia of Lumbricus), and the enteronephric micronephridia (e.g. the septal and the pharyngeal nephridia of
P h e r e t i m a and the pharyngeal nephridia of Lampito)
and enteronephric meganephridia (e. g. the meganephridia of
Lampito). It is this last type that is described for the first
time in this paper.
70
&ARM NAHAYAN BAHL
I have discussed in section 5 of this paper the question as
to whether we should at all retain the terms ' micronephridia '
and ' meganephridia ', and have suggested that the classification of nephridia in Oligochaetes should be based not on their
size but on their place of opening, i. e. the nephridia should
be classed as ' exonephric ' or ' enteronephric ', and not as
micronephridia or meganephridia.
2. HISTORY OF OUR KNOWLEDGE OF THE GENUS
LAMPIIO.
This earthworm was first described by Kinberg in 1867,
and was named by him L a m p i t o m a u r i t i i . Since then
almost all the well-known systematists on earthworms, e.g.
Miehaelsen, Beddard, Eosa, Bourne, Perrier, and L. Vaillant,
have described this earthworm, but not under the original name
given by Kinberg. The name Lampito m a u r i t i i was
ignored. The result is that the worm has been described, more
or less incompletely, under about ten names. The synonyms
are as follows :
Beddard.
1. P e r i c h a e t a m a u r i t i i .
2. P e r i c h a e t a coerulea and P. 1 uzonica.
3. P e r i c h a e t a a r m a t a .
4. Megascolex m a d a g a s c a r e n s i s .
Miehaelsen. 1. Megascolex m a u r i t i i .
2. Megascolex a r mat us.
3. P e r i c h a e t a m a d a g a s c a r e n s i s .
1. Megascolex arm at us.
Rosa.
Bourne.
1. P e r i c h a e t a b i v a g i n a t a and P. s a l a t t e n s i s.
Beddard, in his monograph on the Oligochaeta (1895), apparently describes this worm under the name of Megascolex
a r m a t u s, but makes no mention of the condition of nephridia
in it. Miehaelsen (7), in the Oligochaete A'olume of the
' Tierreioh ' (1900), united Kinberg's genus Lampito with
Megascolex, and described this worm under the name of
ENTEBONBPHRIC NEPHRIDIATj SYSTEM IN EARTHWORMS
71
Megascolex m a u r i t i i . He gives a description of the
nephridia in the following words : ' Ausser den diffusen Nephridien 1 Paar Meganephridien in den Segm. des Mittelkorpers
von 19 an.' Later, in 1909 (9), in consequence of finding two
other worms which agreed with Lampito m a u r i t i i in the
possession of this peculiar form of nephridial system—micronephridia throughout the body and meganephridia in addition
in the post-clitellar segments—Michaelsen considered it justifiable to constitute a separate genus Lampito for these
worms, and in so doing he altered Kinberg's original definition
of the genus. In 1916 (10), however, Michaelsen again merged
Lampito into the larger genus Megascolex, since he
came to believe that the coexistence of micro- and meganephridia had no special systematic importance. He says ;
' Ich habe friiher wegen der Ausstattung mit Meganephridien
neben Micronephridien die Gattung L a m p i t o Kinb. von
'Megascolex abgetrennt. Meine verbesserte Anschauung
tiber die systematische Bedeutung dieser Organisation veranlasst mich, diese Gattung Lampito wieder einzuziehen und
ihre Arten in die Megascolex einzureihen.' According to
Michaelsen's latest view, therefore, L a m p i t o is identical
with Megascolex, and all the species of L a m p i t o become
species of Megascolex.
But the existence of an ' enteronephric ' type of nephridial
system in all the species comprised till lately under the genus
L a m p i t o is bound to affect its systematic position and to
bring it close to the genus P e r i c h a e t a (Pheretima) in
which such an excretory system is already known to exist.
The possession of this type of excretory system would not
only cut off L a m p i t o from the other species of Megascolex but would also separate it from the purely meganephric genus P e r i o n y c h e l l a to which Michaelsen thought
L am p i t o was closely allied (9). I have considered it advisable
and convenient to keep L a m p i t o separate from Megascolex, and to leave it to the systematists to determine
whether or not a deep-seated anatomical difference, such as
there exists between the ' exonephric ' and ' enteronephric '
72
KARM NARAYAN BAHL
types of nephridial system, is enough to separate even now the
erstwhile distinct genera Lampito and Megascolex.
Five species of the genus Lampito have so far been
described, namely (1) Lampito m a u r i t i i (Kinberg),
(2) L a m p i t o v i l p a t t i e n s i s (Michaelsen), (3) Lampito
sylvicola (Michaelsen), (4) Lampito t r i l o b a t a (Stephenson), and (5) Lampito dubius (Stephenson). My Colombo
specimens belong to Stephenson's species L. t r i l o b a t a ,
which he records from Baroda (12). Specimens from Bangalore1
were undoubtedly L. m a u r i t i i , and so were specimens
from Madras. My Delhi specimens seemed immature; they
had no visible external genital openings or papillae, &c, and
the prostates were very small or undeveloped. I have consequently abstained from using these worms for work in
connexion with this paper.
3.
THE
NEPHRIDIAL
SYSTEM
OF
L A M P I T O .
(a) The General Plan of the System.
The nephridial system of Lampito, like that of Pheret i m a, consists of three sets of tubules, each with its own system
of ducts.
(1) The first set comprises a pair of meganephridia, one on
each side, in every segment of the worm behind the 19th.
These meganephridia are the largest and the most prominent
of the three kinds of tubules. They have a pre-septal funnel
and the body of the nephridium lies in the segment following the
one containing the funnel. They do not open to the exterior
on the skin, but discharge their excretory products in each
segment into a pair of septal excretory canals which in their
turn empty themselves into a median supra-intestinal excretory
duct. This latter duct runs longitudinally along the dorsal
side of the intestine and opens into the intestinal lumen at
segmental intervals. These nephridia are therefore described
as the ' enteronephric meganephridia '.
(2) The nephridia of the second set are the integumentary
1
I am indebted to Professor C. R. Narayan Rao for these specimens.
ENTEHONEPHRIC NEPH1UDIAL SYSTEM IN EARTHWORMS
73
micronephridia. These are very much smaller than the meganephridia, and are, in fact, about one-sixth their size. They
lie in the anterior portion of each coelomic chamber attached
to the inner surface of the body-wall just behind the intersegmental septa. They are found in all the segments except
the first fourteen, and behind the nineteenth segment coexist
with the meganephridia of the first set. Like the integumentary
nephridia of P h e r e t i m a , these micronephridia of Lampito
also open separately on the body-wall through nephridiopores.
I have described these nephridia as the ' exonephric micronephridia '.
(3) The nephridia of the third set are the so-called ' pharyngeal nephridia ' that lie as paired tufts on each side of the
oesophagus and gizzard in the fifth, sixth, seventh, eighth,
and ninth segments. The ductules of these nephridia run
forward in separate bundles ventro-laterally to the oesophagus and open anteriorly into the second, third, and fourth
Begments.
The general plan of the nephridial system, including the
meganephridia, the micronephridia, and the pharyngeal
nephridia, together with their respective ducts, is shown in
Text-fig. 1.
(b) The E n t e r o n e p h r i c Meganephridia.
The enteronephric meganephridia correspond in position to
the nephridia of Lumbricns and are similarly distributed. In
L a m p i t o these nephridia do not occur in the anterior nineteen segments but are present in all the succeeding ones, a pair
in each segment (Text-fig. 1). Each nephridium consists of
two portions—a post-septal body and a pre-septal narrow
anterior prolongation ending in the funnel. The pre-septal
funnel lies in a ventral position on each side of the nerve-cord
close to the place where the septum joins the body-wall. It
is followed by a long narrow ductule which perforates the
septum behind and is continued as the nephridial canal in
the post-septal portion, i. e. the body of the nephridium. The
funnel presents some very interesting features within the
KARM NARAYAN BAHL
TEXT-FIG. 1.
Ph
S.N.
The general plan of the neplmdial system in L a m p i t o t r i l o b a t a .
D.V., dorsal vessel; Giz., gizzard; I.N., integumentary
nephridia; Oe., oesophagus; Pdv, Prf2., Pd3., PdA., Pdr,.
sheaves of ductules of the pharyngeal nephridia of the fifth
sixth, seventh, eighth,
and ninth segments; -P.iV,., P.N^.
P.iV3., P.Nf., P.AT5., the pharyngeal nephridia of the fifth, sixth
seventh, eighth, and ninth segments ; Ph., pharynx ; Si.e.d.
aupra-intestinal excretory duct; S.N., septal nephridia.
ENTERONEPHRIC NEPHRIDIATJ SYSTEM IN EARTHWORMS
75
sub-genus L a m p i t o , and seems to throw some light on the
origin of the multiple nephridia of P h e r e t i m a .
• The disposition of these meganephridia in relation to the
other organs of the worm is shown in Text-fig. 1 and PI. 2,
fig. 1, and the course of the nephridial canal is sketched in
PL 2, fig. 2. From an examination of thesefigures,it becomes
clear that while in general disposition these meganephridia agree
with those of Lumbricus, in their structure, in the course
of their nephridial canals, and in their ducts and openings,
they closely resemble the ' septal nephridia ' of P h e r e t i m a .
In fact, the meganephridia of Lampito are so closely
associated with the intersegmental septa that they can appropriately be described as the ' septal nephridia ' of L a m p i t o .
The septa support not onty the coelomic funnels of these
nephridia but also their terminal ducts, which lie on them as
the septal excretory canals (vide infra).
As is the case with the nephridia of most earthworms, the
canal of the nephridium in Lampito consists of a large
number of perforated or drain-pipe cells placed end to end, and
is intracellular. The canal is ciliated at several places, but my
observations on the ciliation of the nephridium are not complete, as I have not been able to examine the nephridia in
the fresh condition.
I shall now describe in some detail the structure of the small
pre-septal portion and the much more extensive post-septal
portion of the meganephridium.
I. The P r e - s e p t a l P o r t i o n .
Each meganephridium commences with a bulbous swelling,
the funnel, which together with a short ciliated tube forms
the pre-septal portion. The funnel is a bilabiate structure, the
upper lip being very large and of the shape of a hood. The
nephrostome or the mouth of the funnel is a narrow, slit-like
transverse opening on the ventral surface, and leads into the
ciliated tube of the first portion of the nephridium. The
upper lip is made up of a large c e n t r a l cell bounded by
a number of marginal cells. The central cell occupies the
76
KARM NARAYAN BAHL
greater part of the area of the upper lip and contains a large
and prominent nucleus. The outer margin of the central cell
is bounded by twenty-eight to thirty marginal cells, each of
which has a rounded nucleus and an elliptical A'acuole in it.
All the marginal cells are equal in size and are set in an incomplete circle round the terminal aperture of the funnel, i. e. the
nephrostome, thus forming the margin of the upper lip. The
marginal cells are profusely ciliated over their terminal and
centrally directed faces ; the cilia are long and closely set,
and in whole preparations they are seen not only surrounding
the top of the funnel like a halo but also entering the nephrostome in the form of long bushy processes.
The lower lip has a slightly convex border and is much
thicker than the upper lip. In L. m a u r i t i i it is made up
of a large number of thickly set cells. They form a very
compact structure and no boundaries can be seen separating
the cells from one another, their number being inferred from
the number of nuclei. If we follow the narrow ' ciliated tube '
forward from the septum to the funnel, we see the tube "with
nuclei alternating on its two walls. Just behind the lower lip
the two walls diverge, and their diverging ends form the two
ends of the lower lip on the ventral surface. The lower lip
lies opposite the central cell which extends forwards, and
together with the marginal cells forms the dorsal portion or
the projecting upper lip of the funnel. The drain-pipe cells
surrounding the nephridial canal becoine continuous, in the
funnel, with the compact cells of the lower lip on the one hand
and with the central cell surrounded by marginals on the
other. The actual mouth of the funnel establishing a communication between the coelom and the nephridial tube is
placed between the inner edge of the central cell on one side
and the front edge of the lower lip on the other.
The funnel differs in appearance and structure in the three
species L. m a u r i t i i , L. t r i l o b a t a , and L. d u b i u s ,
and these differences can be realized on an examination of
figs. 3-7 (PI. 2). While in the first two species it is largely
a matter of size, the funnel and the nephridium as a whole
ENTERONBPHRIC NEPHRIDIAL SYSTEM IN EARTHWORMS
77
being larger in L . m a u r i t i i than in L . t r i l o b a t a , in
L . d u b i u s , on the other hand, Stephenson (13) describes
a cluster of funnels to each meganephridium (PI. 2, fig. 7).
Each meganephridium here has about half a dozen funnels,
and ' one might say that the meganephridia are here caught
in the act of dividing up '. In L . m a u r i t i i the funnel is
reniform, about 15/u. in its long and 8/x in its short diameter,
so as to be about twice as wide from side to side as from anterior
to posterior end. The anterior margin of the funnel is indented
in the middle, and is thus distinguished from the funnel in
L . t r i l o b a t a , where there is no such indentation and where
the funnel is almost rounded, 8/*x7^ being about half the
size of the funnels in L . m a u r i t i i .
The ' ciliated tube ' between the funnel and the septum is
surrounded by a mass of vesicular cells which are really a
group of coelomic epithelial cells (PI. 2, fig. 3). Benham
figures this mass of cells behind the funnel in L u m b r i c u s
in Text-figs. 1 and 2 (6). The ' debris ' of coelomic corpuscles
described by Benham as being a constant feature of the funnel
of L u m b r i c u s , is also frequently met with on the funnel
of L a m p i t o , but it is by no means constant. The tube
has two rows of cilia which present the appearance of a
wavy line along the axis of the tube where the cilia of the two
sides meet (PI. 2, fig. 3). They drive the coelomic fluid from
the funnel into the body of the nephridium.
A remarkable feature of the funnel in L . m a u r i t i i and
L . t r i l o b a t a is that, although the nephridium in each of
these two species has a single funnel, there are always one or
more masses of cells projecting from the ' ciliated tube ' following the funnel (PI. 2, figs. 3 and 4, mm.). In L. m a u r i t i i
there is a single large mass consisting of many cells closely
packed together, but in L . t r i l o b a t a there are two or threecompact masses each with a smaller number of cells than in
L . m a u r i t i i . I have found these masses invariably present
in all the funnels of the two species I have examined. In
sections they are seen as proliferations of the wall of the
' ciliated tube ' as shown in PI. 2, fig. 5, which shows a
78
KAHM NARAYAN BAHL
longitudinal section of the funnel and the ' ciliated tube ' in
L. t r i l o b a t a .
This fact of the presence of these solid masses on the wall
of the nephridial tube of these two species, taken in conjunction
with the presence of half a dozen funnels on the nephridium
of L. d u b i u s , becomes very significant. The question
arises as to what these masses represent. In their appearance
and structure they very much resemble embryonic nephridial
masses, and their position leads one strongly to suspect that
they represent either the rudiments (Anlage) or the vestiges
of other funnels. Since it is difficult to conceive of them
as the beginnings of other funnels, they must therefore belong
to the category of ' vestigial structures '. We can say, therefore,
that a condition of multiple funnels of a meganephridium
exists in the sub-genus L a m p i t o ; but that while six welldeveloped functional funnels occur in L. d u b i u s , in the
other two species there is only one functional funnel and one
or more vestiges of additional funnels. It is difficult to explain
how and why this reduction of funnels took place in the
two species L. m a u r i t i i and L. t r i l o b a t a . The
significance of this fact in relation to the general question of
the phylogeny of Oligochaete nephridia I shall discuss in
section 5 of this paper.
A comparison of the funnel in L a m p i t o with that of other
genera is very interesting. In his paper on the nephridium
of Lumbrieus (6), Benham has traced a few stages in the
evolution of the complicated funnel of L u m b r i e u s . He
figures (PL xxiv, fig. 29) four stages in the process of the
complication of the funnel. Starting with the simple funnel
of the Enchytraeidae where it is formed merely of the single
terminal perforated cell, he passes on to the funnel in S t y 1 a r i a
and Glepsine where it consists of two cells. The marginal
cells first make their appearance in E h y n c h e l m i s where
they are eight in number, but their number is greatly increased
in U r o c h a e t a . In the third stage (fig. 29,c), Benham
considers that the intracellular tube gets greatly dilated at its
terminal end so that ' the sides of the tube diverge, the " per-
ENTBRONEPHRIC NEPHRIDIAL SYSTEM IN EARTHWORMS
79
forated ce Is " become ' grooved cells ", and lie between the
intracellular tube and the marginal cells '. This stage has
not been known to be represented by the funnel of any known
earthworm, and Benham remarks, ' I am not sure that any
of the earthworms studied correspond to this stage.' The
fourth stage is represented by E h i n o d r i 1 us and Lumb r i c u s, in which there is a still further opening out of the
intracellular tube and an outward curving of the ' grooved
cells '. From the structure of the funnel in Lam pi to it is
clear that it represents the third or missing stage of the series
in the evolution of the complicated funnel of L u m b r i c u s ,
since in L a m p i t o , although the intracellular tube is greatly
dilated at its entrance into the funnel and its sides widely
diverge, there is no outward curving of these diverging ends
as in L u m b r i c u s . With the filling of this gap, the series
of four funnels given by Benham in fig. 29 of his paper
becomes a real complete series showing the gradual complication and differentiation of the funnel.
The funnel in L a m p i t o , therefore, is simpler or less
differentiated than that of Lumbricus and represents
a lower stage in its evolution.
II. The P o s t - s e p t a l P o r t i o n .
The post-septal portion or the body of the nephridium
(PI. 2, fig. 2) comprises a long and narrow straight lobe (S.L.)
and a partially twisted loop (T.L.) of about the same length
as the straight lobe running parallel to it. Both the lobe
and the loop begin from the mid-ventral line and run outwards
and upwards towards the mid-dorsal line. The straight lobe
is free and rounded at one end, while at the other it is continued
into the distal limb of the twisted loop. Each of the two limbs
of the loop, the proximal and the distal, carries three nephridial
canals in it, and the two limbs are generally twisted round
each other in their distal halves, the number of spiral twists
varying from two to five. The straight lobe has two pairs of
parallel canals running through its body, and these canals are
continuous with those of the twisted loop at its lower end.
80
KARM NARAYAN BAHL
The lobe is, on an average, 1-96 mm. in length and 121ju in
thickness ; the twisted loop has about the same length, but
each of its limbs is only about 90/z in thickness.
The ' ciliated tube ' after perforating the intersegmental
septum becomes incorporated into that limb of the twisted
TEXT-FIG. 2.
T.L
S.I.
A septal and an integumentary nephridium from L a m p i t o
m a u r i t i i . A, a septal nephridium. B, an integumentary
nephridium. S.L., straight lobe; T.L., twisted loop; P.L.,
proximal limb; D.L., distal limb; f, funnel; f.n.t., the
free first part of the nepliridial tube ; T.N.D., the terminal
nephridial duct.
loop which I have called the proximal (P.L.) to distinguish
it from the other or the distal limb (D.L.), which is continuous
with the straight lobe. The exact course of the nephridial
canal after it has entered the body of the nephridium will be
more readily understood by a glance at PI. 2, fig. 2, than by
a verbal description which becomes unnecessary. We may
note, however, that the proximal limb of the twisted loop
not only receives the ' ciliated tube ' below the funnel, but
that the terminal duct leaves the nephridium by the same limb.
ENTERONBPHRIC NEPHRIDIAL SYSTEM IN EARTHWOEMS
81
The lower end of the proximal limb, therefore, forms the place
both of entrance and exit of the nephridial canal.
The canal is almost uniform in diameter for most of itslength, but towards its last part it enlarges and hence we find
that the diameter of the terminal duct is about three times
that of the ' ciliated tube '. The only part of the nephridium
of the ciliation of which I am sure is the first part of the canal,
i. e. the narrow ciliated tube between the funnel and the body
of the nephridium. In microscopic preparations from preserved
specimens I have not been able to make out the cilia in any
other part of the nephridium, but it is quite possible that there
are other ciliated tracts in the nephridium which can only be
distinguished property in mounts of fresh material.
On comparing the septal nephridium of L a m p i t o with
that of Pheretirna, we find that while in P h e r e t i m a ,
the twisted loop is about twice the length of the straight lobe,
the two are of about the same size in L a m p i t o ; while in
P h e r e t i m a the distal half of the twisted loop carries only
two canals in each of its two limbs, in Lampito there are
three canals in each of the two limbs throughout their length.
Moreover, the septal nephridia of P h e r e t i m a have either
a pre-septal or a post-septal funnel, while in L a m p i t o the
funnel is always pre-septal. In section 5 I have discussed the
question as to whether the single septal nephridium of Lampito is to be regarded as the equivalent of 80-100 septal
nephridia of a segment in P h e r e t i m a , the latter having
been derived by a process of branching from the former.
(c) The Ducts and Openings of the E n t e r o n e p h r i c
M e g a n e p h r i d i a.
(1) The Septal E x c r e t o r y Canal.—In their general
outline the ducts and openings of the meganephridia resemble
those of the septal nephridia of P h e r e t i m a . The terminal
duct of each meganephridium does not open out on the skin
but travels along the posterior face of the septum in front of
it and runs towards the mid-dorsal line to join the supraintestinal excretory duct (PL 2, fig. 1). Since there is a pair
NO. 269
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KAEM NARAYAN BAHL
of meganephridia in each coelomic chamber we get a pair of
septal excretory canals, one in each half of the septum, right
and left. Unlike what occurs in P h e r e t i m a , where the
terminal ducts of the several nephridia join together to form
a septal excretory canal, in L a m p i t o each meganephridium
gives rise to one septal excretory canal; in fact, the septal
excretory canal is merely a continuation of the terminal duct
of the meganephridium behind it.
The septal canal is a fairly prominent structure on the
posterior face of each septum ; it is easily seen on dissection
under a binocular dissecting microscope. It starts ventrally,
on both the right and left sides, at the place Avhere the ciliated
duct following the funnel perforates the septum, since it is
here that the terminal duet of the nephridium gets attached to
the septum and travels tlorsahvards. The canal follows a wavy
or zigzag course for the greater part of its length as shown
in PI. 2, fig. 1, and enters the supra-intestinal exaretory duct
ventral to the place where the dorso-lateral vessel enters the
dorsal vessel. The average diameter of the canal is 35/a, and
its average length from its point of attachment to the septum
to the point Avhere it enters the supra-intestinal duct measures
2-8 mm. in L. m a u r i t i i . The canal is thin-walled and is
non-ciliated throughovit.
(2) The S u p r a - i n t e s t i n a l E x c r e t o r y Duct.—The
supra-intestinal excretory duct is a longitudinal channel
•situated in the mid-dorsal line beneath the dorsal vessel and
•above the intestine. It is closely attached to—almost embedded
in—the dorsal wall of the gut but can be separated by a careful
dissection. Unlike the supra-intestinal ducts of P h e r e t i m a ,
the excretory duct of L a m p i t o is very narrow in diameter,
and consequently it is not a prominent structure in sections
and has to be looked for carefully. This median excretory
duct begins from septum 19/20, this being the first septum
which bears a meganephridium and a septal canal, and is
•continued along the entire length of the gut from septum 19/20
to the posterior end of the body of the worm. The average
diameter of the lumen of the supra-intestinal duct is 44 //,
ENTERONEPHRIC NEPHRID1AL SYSTEM IN EARTHWORMS
bd
while that of the dorsal vessel is 237/n. In the region of each
intersegmental septum its pair of septal excretory canals
enter the supra-intestinal excretory duct, so that the excretory
fluid from the septal canals is discharged into the mid-dorsal
channel at each intersegmentum.
Following the clue afforded by intersegmental openings of
the supra-intestinal excretory ducts into the gut in P h e r e t i m a , I prepared a complete series of sections passing through
four segments of L a m p i t o , and in this series I found
exactly four pairs of communications between the supraintestinal excretory duct and the lumen of the intestine. The
openings of this mid-dorsal duct into the gut are situated on
the typhlosole on its right and left borders. The typhlosole
is a short blunt process (PI. 2, fig. 8) and in sections presents
two well-marked side-walls, and it is on these side-walls that
the excretory duct opens in each intersegmentum. In PI. 2,
fig. 1, I have shown two narrow ductules leading from the
supra-intestinal duct to the lumen of the gut. These ductules
are very narrow and measure about Sfj, in width in sections.
It will be noticed that I have shown a pair of ductules leading
from the excretory duct into the lumen of the intestine, one on
the right and the other on the left wall of the typhlosole. In
P h e r e t i m a p o s t h u m a , however, where there are two
supra-intestinal ducts I have recorded (1) ' that the supraintestinal ducts do not both communicate with the gut in
each intersegmental place, but it is always only one of them—
sometimes the right and sometimes the left—which does so.
In a series of sections passing through seven intersegmental
places the ducts opened into the gut antero-posteriorly in the
following order : left, left ; right, left, right, right, right.'
In P h e r e t i m a r o d r i c e n s i s , on the other hand, there is
a single supra-intestinal excretory duct, but this duct gives out
a pair of ductules in each segment to the lumen of the intestine.
We have just seen that the condition is the same in L a m p i t o .
The condition of these ductules in L a m p i t o and P h e r e tima r o d r i c e n s i s , therefore, varies in detail from that in
P h e r e t i m a p o s t h u m a , the former having a pair of
G2
84
KABM NARAYAN BAHL
ducfcules and the latter a single one leading from the median
excretory duct into the lumen of the gut in each intersegmentum.
It is a minor difference but still worth noting. The presence
of small projections of the walls in the supra-intestinal ducts
constitutes an interesting feature of the excretory channels
of L a m p i t o , a feature not indicated in P h e r e t i m a .
Their disposition is shown in PI. 2, fig. 12. It is difficult to say
what their function can be, but the fact that they are more
numerous opposite point of entrance of each septal canal into
the dorsal excretory duct than between the successive pairs
of septal canals leads one to suspect that they may act as
valves allowing excretory fluid to pass into the dorsal duct
but not back into the septal canals.
(tZ) The E x o n e p h r i c (Integumentarj^) M i c r o n e p h r i d i a.
The integumentary nephridia are V-shaped structures
attached to the inner surface of the body-wall, or, in other
words, to the somatic layer of the coelomic epithelium. They
are absent in the first fourteen segments of the worm but are
present in all the succeeding ones. In each segment they are
confined to its anterior portion only and lie immediately behind
the intersegmental septa, but they extend all along from the
mid-ventral to the mid-dorsal line. They are thickly set and
are not arranged in any definite order. They can be made out
with difficulty in a fresh specimen, but can be easily recognized under a binocular microscope in preserved specimens.
These nephridia are extremely minute organs, but resemble
the large enteronephric septal nephridia in structure except
in their lack of a funnel. Like the septal nephridia they also
consist of a straight lobe and a twisted loop, and each of these
two parts contains the nephridial canal disposed in a manner
similar to what obtains in the septal nephridia. The two limbs
of the V which are unequal in size, one being about one-third
the length of the other, represent the straight lobe and the
twisted loop respectively, the nephridia being attached to the
body-wall by the terminal duct coming out of the twisted
ENTER0NEPHR1C NEPHRIDIAL SYSTEM IN EARTHWORMS
85
loop. Each nephridium opens to the exterior on the body-wall
by a separate nephridiopore. As already mentioned, these
nephridia are very minute, and are one-sixth the size of a
septal nephridium. A nephridium of an average size has its
straight lobe about 114ft in length, and the twisted loop about
340;u in length. They do not possess any funnel, and because
of their minuteness it is difficult to make out how the nephridial
canal ends internally. In segments possessing septal nephridia
the number of integumentary nephridia is not very large ;
I found 40-50 nephridia in the twenty-third and twentyfifth segments. But in the clitellar segments (15-17) the
number is very large, and we find the nephridia forming
a thick row behind the septa in each of these four segments—
each row containing about a hundred to a hundred and twentyfive nephridia—thus giving 200-250 nephridia in each of these
segments. Bach nephridium is a separate discrete structure
and opens by its duct to the exterior on the skin. There is no
network of any kind formed by the tubules of separate nephridia.
As will be noticed below, these nephridia resemble closely the
pharyngeal ones both in their size and their structure (PL 2,
% 9).
(e) The P h a r y n g e a l X e p h r i d i a and t h e i r D u c t s .
The pharyngeal nephridia in L a m p i t o occur in tufts in the
fifth, sixth, seventh, eighth, and ninth segments. There is a
pair of these tufts in each of the segments named, and they
lie on each side of the oesophagus and gizzard. These tufts
of nephridia are not visible at first on a mid-dorsal incision,
since they are hidden beneath the intersegmental septa which
are specially large and thick in this region and are stretched
backwards forming a series of cones, one inside the other, round
the oesophagus and gizzard. These septa have therefore to
be removed to a large extent to display the pharyngeal
nephridia. The general disposition of these pharyngeal
nephridia and their ducts is shown in Text-fig. 1, from which
it will be seen that the ducts lead into the cavity of the pharynx
and hence the name pharyngeal nephridia.
86
KARM NABAYAN BAHL
Iii a previous paper on the nephridia of P h e r e t i m a (1)
I have referred briefly to the literature on the subject of
pharyngeal nephridia; I have quoted therein Miss Raff (11),
who found that in Megascolex dorsalis and Megascolex fielderi, the pharyngeal nephridia opened not
into the pharyngeal caA'ity but to the exterior. It is therefore
remarkable to find in the three species of Megascolex
(L a m p i t o) I have examined pharyngeal nephridia with their
ducts opening into the pharyngeal cavity. It seems difficult
to believe that the pharyngeal nephridia would open to t h e
e x t e r i o r in some and in the p h a r y n g e a l c a v i t y in
other species of the same genus. The nephridia and their ducts
in L a m p i t o differ from those of P h e r e t i m a in two
important particulars. In the first place, the pharyngeal
nephridia in L a m p i t o have a much greater extent than in
an}r other earthworm in which these organs have hitherto been
described; they extend over five segments (fifth to ninth, both
inclusive) and occupj'- a considerable area in each of these
segments. In the second place the ductules of individual
nephridia do not unite together to form a common duct for
each tuft as happens in P h e r e t i m a , but these ductules
run forward to the pharynx parallel to one another, forming
a sheaf. They are closely apposed together (PI. 2,fig.10) but
do not open into one another, and each ductule of a bundle
opens separately into the lumen of the pharynx (PI. 2,fig.11).
The pharyngeal tufts of nephridia look like bunches of strings
(P.Nj.-P.N5.) and are disposed in two semicircular curves
round the oesophagus, each curve extending from the midventral to the mid-dorsal line. Posteriorly these nephridial
masses are loosery attached to the septa immediately behind
them. The bundles of ductules (PdL.-Pdd.) originating from
these nephridial tufts run forward and open into the cavity
of pharynx in the second, third, and fourth segments. As
regards the structure of each pharyngeal nephridium, we may
note that it is a micronephridium with a structure very similar
to that of an integumentary nephridium (PL 2,fig.10). Like
the latter, it consists of a straight lobe and a twisted loop,
ENTERONEPHRIC NEPHRIDIAL SYSTEM IN EARTHWORMS
87
the proximal limb of the latter being continued out as the
terminal nephridial duct which forms one of the ductules
of the pharyngeal ducts. There are no funnels to these
nephridia, and it is difficult to say whether they are excretory
or peptic in function. Beddard has applied the term ' peptonephridia ' to those that open into the anterior section of the
alimentary canal and function in relation to digestion. The
first part of the definition applies well to these pharyngeal
nephridia, but it is problematic whether the second part
does so.
The pharyngeals, like the integumentary nephridia, have no
funnels ; both kinds of nephridia are equal in size and both
consist of a short straight lobe, a long twisted loop, and a
terminal duct coming out of the latter.
4.
THE BLOOD-SUPPLY OF THE NEPHRIDIA IN L A M P I T O .
In a previous paper (1) in this journal I have described the
blood-supply of the nephridia in P h e r e t i m a , and since
L a m p i t o closely resembles P h e r e t i m a in its nephridial
system, the blood-supply of its nephridia is also similarly
arranged.
The paired branches, called the parietals, given off from
the ventral vessel in each segment, perforate the septa
behind them and run along the middle line of the body-wall
of the succeeding segment ventro-dorsally. These parietal
vessels give off small branches all along their course and
supply blood to both the septal and the integumentary nephridia
of the segment following the one in which they come out of
the ventral vessel (e. g. the pair of parietal vessels leaA'ing the
ventral in the twentieth segment perforate the septum 20/21
and distribute blood to the septal and integumentary nephridia
of the twenty-first segment). The pharyngeal nephridia, on
the other hand, receive their supply of blood from the dorsal
vessel, since that is the main channel for distribution of blood in
the anterior region. L a m p i t o has no subneural vessel and,
consequently, the commissural vessel connecting the dorsal
with the subneural vessel in P h e r e t i m a (2) here lacks
88
KABM NARAYAN BAHL
a ventral connexion. Moreover, the commissural does not lie
on the septum as it does in P h e r e t i m a , but lies alongside
the septum on the body-wall and perforates the septum to
enter the dorsal vessel. The branches of the commissural
receive blood from the septal and integumentary nephridia
and carry it to the dorsal vessel. The blood from the pharyngeal nephridia is taken back to the main longitudinal channels
through branches leading to the lateral-oesophageals in the
pre-clitellar segments of the animal.
5. DISCUSSION.
There are several questions of interest that arise in connexion with the results of the present investigation, and in
this section I propose to deal with three of them, namely
(a) the classification of Oligochaete nephridia, (b) the significance of multiple funnels or their vestiges in species of
L a m p i t o , and lastly (c) the systematic position and distribution of the genera Megascolex and P h e r e t i m a .
(a) On the Classification of Oligochaete Nephridia.
Systematists divide the Oligochaete nephridia into two
groups, the micronephridia and the meganephridia. This
classification, due probably to Michaelsen in the first instance,
is purely arbitrary inasmuch as it depends merely on size to
which there are no well-defined limits for either one category
or the other, and brings the subjective element of the observer
in descriptions of nephridia. For instance, Stephenson (14)
describes the nephridia of Megascolides p r a s a d i in the
following words : ' Behind the clitellum the micronephridia are
arranged in transverse rows of about eight to ten on each
side ; in the clitellar region they are also in transverse rows,
and somewhat larger ; in front of this they are sparser, and
their arrangement is less regular. About forty segments from
the hinder end the innermost nephridium on each side in each
segment enlarges, and this condition is maintained to the end ;
there is thus a longitudinal row of larger nephridia on each
ENTERONEPHRIC NEPHRIDIAL SYSTEM IN EARTHWORMS
S9
side of the ventral nerve-cord, but I do not think that these
could be described by any one as meganephridia—only as
enlarged micronephridia.' Michaelsen (8), on the
other hand, describes the nephridia of Megascolides in
general as ' vorn rein plectonephridisch, im Hinterko'rper
Meganephridien neben diffusen N e p h r i d i e n ' . It
is clear that Michaelsen describes as meganephridia -what
Stephenson calls merely ' enlarged micronephridia '. In fact
in Megascolides, one kind easily passes into the other.
But since size is not an anatomical character, the classification of nephridia on the basis of size alone has very little to
commend itself. Nor does this system of division imply any
genetic distinction. The possession by two earthworms of
a micronephridial system implies no close relationship between
them nor does the relationship become distant or non-existent
between two Avorms, one of which possesses a micronephridial
and the other a meganephridial system. The distinctive
character is not structural and implies no well-defined contrast
between two groups. In fact in several cases both micronephridia and meganephridia have been found to occur in the
same earthworm and in the same segment (e.g. Lampito).
Moreover, since there is little difference in s t r u c t u r e between
micronephridia and meganephridia, the distinction breaks down
in an important essential.
I suggest, therefore, that the basis of classification should
not be the size but the place of opening of the nephridia, and
consequently the division should be into the exonephric and
enteronephric types of nephridia, according as they open to the
exterior or into the gut. This distinction is based on a structural
character of fundamental importance, and since the enteronephric system is a deep-seated elaborate anatomical feature,
it is very probable that earthworms with an enteronephric
system would form a genetic unity by themselves. If this be
so, our classification would have the merit of being based not
only on an anatomical character but also on phylogenetic
relationship. Each of these two types of nephridia could be
further classified into open and closed nephridia according as
90
KARM NABAYAN BAHL
they possess or lack a funnel. Closed nephridia, referred to
generally as protonephridia in worms, are fairly common
amongst the Polychaetes and are well recognized, but I do not
think that sufficient attention has been paid to this closed tjrpe
of nephridia in Oligochaetes. The genus intensively studied
in this group being Lumbricus possessing an open funnel,
it is generally assumed that the nephridia of all earthworms
have funnels opening internally into the coelom. Nephridia
with closed internal ends are not generally known in the
Oligochaetes. Nevertheless it is now a fact that most of the
nephridia hitherto described as micronephridia are really closed
nephridia without funnels. The integumentary and pharyngeal
nephridia of P h e r e t:. m a and L a m p i t o are examples so
to speak, close at hand, besides many others. It is not j-et
known what exactly the structure of the closed inner ends of
these nephridia is ; but this much is certain, that these nephridia
have no open funnels. On the other hand, we have only
recently recognized the funnels of the septal nephridia (micronephridia) of P h e r e t i m a , while the funnel of the nephridium
of L u m b r i c u s is, so to speak, a classical object of study.
We can illustrate our new classification in a tabular form as
follows :
Oligoohaete nephridia.
I "
I
Exonephiic.
1. Open.
2. Closed.
Enteronephric.
3. Open.
4. Closed.
Examples of these four types of nephridia are these :
1. Ordinary septal nephridia of L u m b r i c u s .
2. Integumentary nephridia of P h e r e t i m a , L a m p i t o ,
Megascolex, &c.
3. Septal nephridia of P h e r e t i m a and L a m p i t o .
4. Pharyngeal nephridia of Pheretima 1 and L a m p i t o .
Of these four kinds, the nephridium of L u m b r i c u s has been
studied intensively, and it has also been known that scattered
ENTEHONEPHRIC NEPHEIDIAL SYSTEM IN EARTHWORMS
91
mtegurnentarynephridia in earthworms open on the body-wall by
separate nephridiopores. I am partly responsible for the knowledge of the last two types of nephridia that open into the gut.
In the present state of our knowledge of Oligochaete nephridia,
I would not maintain that all earthworms possessing the enteronephric type of nephridial system have a common origin, nor
would I contend that this type of excretory system is a structural
convergence due to the physiological needs of the worms possessing it. But it is evident that for purposes of classification of
these nephridia, the place and manner of their opening is a
much more appropriate character than mere size, and that if
the former are made the basis of classification we shall gain
a more accurate and detailed knowledge of the structure of
nephridia in this group than we have at present, although it
will entail a greater labour on the part of the observer.
(b) On t h e Significance of Multiple F u n n e l s in
Species of L a m p i t o .
In section 3 (b) I have recorded the fact that while in
L a m p i t o dubius Stephenson (13) has described half a
dozen funnels to each meganephridium, in the other two species
of L a m p i t o (e.g. L. m a u r i t i i and L. t r i l o b a t a ) there
is a single functional funnel, but that below this funnel there
are one or more masses of cells which probably represent
vestiges of other funnels (PI. 2, fig. 3). In the genus Lampito,
therefore,, there are multiple funnels to each meganephridium,
one species having all of them functional, while in others one
is functional and the others degenerate and vestigial. So far
as I know L a m p i t o is the only genus in which multiple
funnels or their vestiges are known to exist with each separate
meganephridium. This fact, taken together with the condition
of nephridia in P h e r e t i m a . where we have in each segment
eighty to a hundred septal nephridia—each with its own
funnel—acquires a special significance. Add to this the central
fact of these two being the only genera which are known to
possess an ' enteronephric ' type of excretorj" system. How
can we drive the nephridial system of one from that of the
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KAEM NARAYAN BAHL
other ? Are the two related ? Can we hold that the multiple
septal nephridia of P h e r e t i m a have been derived by
a branching of the large septal nephridia of L a m p i t o , the
early beginnings of which are now seen in L. d u b i u s ?
In a previous paper (3) I have worked out the development of
nephridia in P h e r e t i m a , and have shown that a paired
condition of nephridia precedes in development the multiple
condition of the adult. There is a separation, early in development, between the ' funnel-cell' and the rest of the nephridial
mass, the former giving rise to all the septal nephridia with
funnels and the latter to all the integumentary nephridia without funnels. From these facts I inferred that while the ' funnelcell ' is capable of giving rise both to the funnel and the body
of the nephridium, the nephridial masses of the body-wall
form only nephridia without funnels. Since in L a m p i t o
also we get in each segment a pair of septal nephridia with
funnels and a large miniber of funnelless integumentary
nephridia, we may conclude that here, too, the nephridial masses
are separated off from the ' funnel-cell', and that while the
funnel-cell can regenerate the body of the nephridium and forms
a large funnelled nephridium, the nephridial masses in connexion with the body-Avail cannot regenerate a funnel, and so
remain funnelless. But we have to notice that while in
P h e r e t i m a the funnel-cell divides repeatedly to give rise
to many funnels and many nephridia on each septum, in
L a m p i t o only a single nephridium. is produced on each half
of a septum and this nephridium acquires many funnels,
either all of them functional, or one functional and others
vestigial. I have already referred to what Stephenson (13)
says with regard to the multiple funnels of L. d u b i u s ,
in which ' one might say that the meganephridia are caught
in the act of dividing up '. We may hold that in the family
Megascolecidae there has been going on a process of branching
and multiplication of the nephridia. We notice it first in
Megascolid.es, where in addition to a pair of meganephridia
in the posterior segments, we have a number of micronephridia
in all the segments. In L a m p i t o the integumentary micro-
ENTERONEPHRIC NEPHRIDIAL SYSTEM IN EARTHWORMS
93
nephridia are similar to those in M e g a s c o 1 i d e s, but the
meganephridium in each segment shows branching in the funnel,
and we get meganephridia with a number of funnels., functional
or vestigial. The condition in P h e r e t i m a represents the
culmination of the process, since in this earthworm we have
multiple septal nephridia with funnels and multiple integumentary without funnels.
(c) Geographical D i s t r i b u t i o n and S y s t e m a t i c
P o s i t i o n of
the Genera
Lampito
and
Pheretima.
Michaelsen in his ' Tierreich ' volume (7) gives the distribution of L a m p i t o m a u r i t i i as follows : ' China (Kowloon),
Burma, Borneo, Singapore, Nias, Sumatra, Christmas Island,
East India, Ceylon, Minikoy, Seychelles, Mauritius, Northwest Madagascar, Zanzibar, Philippines, and Cochin-China.'
Stephenson (14), describing the Oligochaeta from the lesser
known parts of India and Eastern Persia, considers L. maur i t i i as being widely distributed in the Indian peninsula.
He writes, 'This worm is one of the commonest in
India—absolutely the commonest in the present collections ;
and being so widely distributed it is scarcely necessary for
the future to note the precise details of each capture.' It will
be seen from the account of these two authorities that this
earthworm is a native of the Oriental Begion, and so far as
is known at present is confined to India and the Eastern
Archipelago. P h e r e t i m a , on the other hand, is a much
more widely distributed genus, and Beddard (5), describing
its distribution, says, ' The most obviously p e r e g r i n e
genus of all those enumerated is P h e r e t i m a , which according
to my experience turns up in almost all gatherings of earthworms from any part of the tropical or even sometimes temperate regions of the world.' He further adds, ' It seems to
be fairly well settled that this extensive genus has its real
home in the islands of the Eastern Archipelago, perhaps
extending a little in various directions from that centre.
But examples of the genus have been found in almost all other
94
KARM NABAYAN BAHL
regions. And what is especially to the point in considering the
facts, the assmnedly peregrine species do not differ from
those found in the real district in which the genus is
indigenous.'
Prom these facts of distribution of the two genera, it is
evident that both belong to the Oriental Eegion and have
a home somewhere in the Eastern Archipelago. The close
relationship established between these two genera because
of their remarkable similarity in the possession of the enteronephric type of excretory system, receives further confirmation from the facts of their distribution. As already mentioned
in section 2, Miehaelsen has included the species of Lamp it o
within the genus Megascolex and in doing so he has
recognized the true affinities of L a m p i t o, since there is no
doubt that he was wide of the mark in considering L a m p i t o
as being nearly allied to P e r i o n y c h e l l a (9). It is now
commonly held that P h e r e t i m a is related to and descended
from Megascolex; in fact, 'the essential characters in
P h e r e t i m a are those of Megascolex, but the gizzard
is farther back, the testes and male funnels are enclosed in
testis sacs instead of being free in the segments (this occurs
occasionally in Megascolex), and on the whole the ring of
setae is more closed up, has smaller gaps in the dorsal and
ventral lines than is usual in Megascolex ' (16). Moreover,
Stephenson (16), in indicating the broad differences between
the Indian and Australian groups of Megascolex, says that
the Australian species are simpler, at a lower level of evolution,
and more uniform, while the Ceylonese species are often
further advanced and in many cases approach P h e r e t i m a .
In view of Avhat we have seen with regard to the excretory
system and distribution of L a m p i t o (Megascolex mauritii), there seems little doubt that these are the species
(M. m a u r i t i i and M. t r i l o b a t a ) which closely approach
P h e r e t i m a . I am strongly inclined to think that the species
hitherto comprised under the genus L a m p i t o and lately
merged into Megascolex by Miehaelsen should be kept
apart and the genus L a m p i t o reconstituted. This genus will
ENTEBONEPHRIC NEPHRIDIAL SYSTEM IN EARTHWORMS
95
form a link between Megascolex on one hand and P h e r e tima on the other, resembling in certain features a typical
Megascolex and in others a typical P h e r e t i m a .
6. MATERIAL AND TECHNIQUE.
As I have already stated, I obtained specimens of L a m p i t o
from Colombo, Madras, and Delhi. The Delhi specimens were
immature, and the work has therefore been carried out with
Colombo and Madras specimens only. The Colombo specimens
belonged to the species L. t r i l o b a t a and the Madras
specimens to L. m a u r i t i i .
Worms were narcotized in weak alcohol—by keeping them
in tap-water in a pie-dish and adding gradually 90 per cent,
alcohol until the alcohol becomes about 7 to 10 per cent, in
strength. I find this method much more satisfactory than
narcotization with ether or chloroform, although it takes
a slightly longer time. For fixation I used Bouin's picroacetic formol, which gives admirable results. In order to obtain
a good fixation of nephridia, worms should be opened in the
mid-dorsal line under water and the flaps stretched out and
pinned, and before the fixative is poured the dissected worm
should be thoroughly washed under the tap. This is necessary
in order to Avash off all coelomic fluid, which, if it remains
surrounding the nephridia, coagulates and renders the fixation
of the latter imperfect. For sectioning worms were kept in
moist cloth for four to six days, after which time the gut is
quite free from earth and the worms can be cut without
injuring the razor. Pieces of worm were stained in bulk in
borax carmine and sections were then counterstaiiied in picronigrosin. For whole mounts of different kinds of nephridia
I used paracarmine.
The three kinds of nephridia, their funnels, the septal excretory canals, and the supra-intestinal ducts were dissected out
under a Zeiss binocular microscope, which has been a very
helpful instrument all along.
96
KARM NARAYAN BAHL
7.
SUMMARY.
1. The ' enteronephric ' type of nephridial system previously
discovered by the author in the genus P h e r e t i m a has now
been shown to be present in the genus L a m p i t o also.
The present investigation extends the distribution of this new
type of excretory system and makes it probable that it occurs
in other genera as well.
2. In essential the nephridial system of L a m p i t o agrees
with that of P h e r e t i m a previously described ; but while
in P h e r e t i m a the 'enteronephric 1 nephridia are minute
and multiple and have been described as micronephridia, these
nephridia in L a m p i t o are large and paired in each segment
and are described as meganephridia.
3. There are three distinct kinds of nephridia in L a m p i t o ,
aamely the septal, the pharyngeal, and the integumentary ;
of these, the septal ones communicate with the lumen of the
gut through an elaborate system of ducts, the pharyngeal tufts
of nephridia open into the pharyngeal cavity through bundles
of ductules, while the integumentaries open on the skin
individually through separate nephridiopores.
4. The septal nephridia of L a m p i t o resembles those of
L u m b r i c u s in their shape and disposition, but in their place
of opening they agree with the enteronephridia of P h e r e t i m a . Therefore both micronephridia (P h e r e t i m a) and
meganephridia (Lanipito) can be ' enteronephric '.
5. Since there is no anatomical difference between microand meganephridia but only a difference in size, this classification of nephridia should be abolished. A better system is to
classify them according to their place of opening and recognize
' exonephric ' and ' enteronephric ' types of nephridia, and
amongst each of these types to distinguish between those that
have an open internal funnel and those in which the internal
end is closed.
6. The septal nephridia of L a m p i t o are characterized
by the presence of multiple funnels to a single nephridium,
and since in some species all the funnels are functional and in
ENTERONEPHRIC NEPHRIDIAL SYSTEM IN EARTHWORMS
97
others one is functional and the others vestigial, it is suggested
that the branching of funnels is a stage leading later to the
multiple nephridia of P h e r e t i m a .
7. Close similarity in their nephridial and other systems
suggests a genetic relationship between the two genera L a m pito and P h e r e t i m a , and the suggestion is supported by
facts of geographical distribution of the two genera. Lampito provides a connecting link between Megascolex and
Pheretima.
8. BEFERENCES TO LITERATURE.
1. Bahl, K. N.—" On a New Type of Nephridial System found in Indian
Earthworms of the Genus Pheretima ", ' Quart. Journ. Micr. Sci.',
vol. 64, pt. i, 1919.
2.
" On the Blood-vascular System of the Earthworm Pheretima
with Remarks on the Course of Circulation in Earthworms ", ibid.,
vol. 65, pt. iii, 1921.
3.
" On the Development of the Enteronephric Type of Nephridial
System found in Indian Earthworms of the Genus Pheretima ",
ibid., vol. 66, pt. i, 1922.
4. Beddard, F. E.—' A Monograph of the Order Oligochaeta '. Oxford,
1895.
5.
' Earthworms and their Allies'. Cambridge, 1912.
6. Benham, W. B.—" The Nephridium of Lumbricus and its Bloodsupply, with Remarks on the Nephridia in other Chaetopods ",
' Quart. Journ. Micr. Sci.', vol. 32, 1891.
7. Michaelsen, W.—' Oligochaeta ' in : Das Tierreich. Leipzig und
Heidelberg, 1900.
8.
' Die geographische Verbreitung der Oligochaeten'. Berlin, 190.1.
9.
" The Oligochaeta of India, Nepal, Ceylon, Burma, and the
Andaman Islands ", ' Mem. Ind. Mus. Calcutta ', vol. 1, no. 3, 1909.
10.
" Result of Dr. E. Mjoberg's Swedish Scientific Expeditions to
Australia, 1910-13", ' X I I I . Oligochaeten'. Stockholm, 1916.
11. Raff, Janet W.—" Contributions to our Knowledge of Australian
Earthworms : The alimental canal, Part I ", ' Proc. Roy. Soc.
Viet.', vol. 22 (N.S.), pt. ii, 1910.
12. Stephenson, J.—" On a collection of Oligochaeta mainly from
Northern India ", ' Rec. Ind. Mus.', vol. 10, 1914.
13.
"On a collection of Oligochaeta belonging to the Indian Museum",
ibid., vol. 12, 1916.
NO. 269
H
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KARM NARAYAN BAHL
14. Stephenson, J.—" On a collection of Oligochaeta from the lesser
known parts of India and from Eastern Persia ", ' Mem. Ind. Mus.',
vol. 7, no. 3, 1920.
15.
" Oligochaeta from Manipur, the Laccadive Islands, Mysore, and
other parts of India ", ' Rec. Ind. Mus.', vol. 22, pt. v, no. 34, 1921.
16.
" Contributions to the Morphology, Classification, and Zoogeography of Indian Oligochaeta ", ' Proc. Zool. Soc.', 1921.
EXPLANATION OF PLATE 2.
Illustrating Professor K. N. BahPs paper ' On the Occurrence of the
" Enteronephric" Type of Nephridial System in Earthworms of the
genus L a m p i t o '.
Fig. 1.—A diagrammatic representation of the ' enteronephric ' S37stem
and its relative position in L a m p i t o m a x i r i t i i . The interseginental
septum lying at right angles to the body-wall is seen from its posterior
aspect, b.w., body-wall; duct., ductules leading from the supra-intestinal
duct to the lumen of the gut; d.v., dorsal vessel; /., funnel; f.n.t., the
free first part of the nephridial tube; g., gut; i.n., integumentary
ncphridia; i.s., intersegmental septum; n.c, nerve-cord; s.e.c, septal
excretory canal; si.e.d., supra-intestinal excretory duct; s.n., septal
nephridium; t.n.d., terminal nephridial duct; tij., typhlosole; v.v.,
ventral vessel.
Kg. 2.—A septal nephridium of L. m a u r i t i i showing the course
of the nephridial tubiile in it. The cilia on the funnel are not shown.
dl., distal limb ; /., the funnel; n.t., nephridial tubule ; n., nephrostome ;
pi., proximal limb ; F.N.T., free first portion of the nephridial tubule;
S.L., straight lobe ; T.L., twisted loop ; T.N.D., terminal nephridial duct.
Fig. 3.—Funnel of a septal nephridium in L a m p i t o m a u r i t i i .
c.c, coelornic cells ; cent., central cell nucleus ; m.c, marginal cells with
vacuoles ; l.l., lower lip ; F.X.T., the free first part of the nephridial
tube ; mm., mass of cells representing a vestigial funnel.
Fig. 4.—Funnel of a septal nephridium in L a m p i t o t r i l o b a t a
showing three masses of cells on the tube of the funnel, mm., vestigial
funnels ; other letters as before.
Fig. 5.—Longitudinal section of the funnel of a septal nephridium in
L a m p i t o t r i l o b a t a . Letters as before.
Fig. 6.—A transverse section of the funnel through its marginal cells.
d., dorsal side ; V, ventral side ; n. m.c, nuclei of marginal cells ; c, cilia;
v., vacuoles.
Fig. 7.—A septal nephridium of L a m p i t o d u b i u s (after Stephenson).
F., funnels of a single nephridium.
Fig. 8.—Part of a transverse section through the body-region of
L a m p i t o showing the ductule leading from the supra-intestinal
ENTERONEPHBIC NEPHRIDIAL SYSTEM IN EARTHWORMS
99
excretory duct into the lumen of the intestine, duct., ductnle establishing
a communication between the supra-intestinal duct and the lumen of
the gut; si.e.d., supra-intestinal excretory duct.
Fig. 8A.—An outline diagram of the transverse section of L a m p i t o ,
structures in the dotted part of which are represented in fig. 8.
Fig. 9.—Integumentary nephridium of L a m p i t o m a u r i t i i . 8.L.,
short straight lobe ; t.l., long twisted loop ; t.n.d., terminal nephridial
duct.
Fig. 10.—Pharyngeal nephridia and their ductules. S.L., short straight
lobe ; t.l., long twisted loop ; duct., a sheaf of ductules leading from the
pharyngeal tufts to the pharynx.
Fig. 11.—A transverse section of L a m p i t o t r i l o b a t a passing
through the pharyngeal region, showing the ductules of the pharyngeal
nephridia entering the cavity of the pharynx, b.iv., body-wall ; d.v.,
dorsal vessel; n.c, nerve-cord; Ph.m., pharyngeal mass; Pdv—Pd!lt
bundles of ductules from the five pairs of nephridial tufts. Pd^ is the
bundle of ductules from the ninth segment, and the individual ductnles
are seen entering the pharyngeal cavity.
Fig. 12.—Portion of the supra-intestinal excretory duct showing the
two septal excretory canals entering it. Outgrowths on the wall, probably
acting as valves, are also shown, s.e.c, septal excretory canal ; sl.e.d.,
supra-intestinal excretory duct; v., valves.
b.'w.
tsi.e.d.
•typhZoaole,
~phj.T71/.
Pd,