A BR&?IUSH-WATER
POLYCIUETE WORM.
387
An Accorint of the Development a i d Breeding-habits of a Brackish-water
Polychaete Worm of the Genus Marphgsa. By R . GOPALAAIYAR,M.A.,
Presidency College, Madras. (Communicated by Dr. E. S. RUSSELL.)
(With 31 Text-figwes.)
[Head 20th November, 1930.1
THEmouth of the Adyar and the piece of backwater near the Madras Volunteer
Guards Rifle Range, south of Mylapore (Madras), offers excellent collectinggrounds to the Marine Biologitjt. Here may be seen during the summer months
from February to September, and in lesser numbers from December to February,
numerous pear-shaped masses of jelly. These masses contain a large number
of tiny black eggs scattered more or less evenly throughout their substance.
When kept in a glass vessel with plenty of water the eggs hatch out readily.
The larva: were kept alive and the changes during their growth into adult
worms were observed and noted down almost daily. Three or four sets of
o;pawn-masses of the same age were kept developing a t the same time and the
various characters as they unfolded themselves were verified in each case.
The following is the result of an investigation carried on for eight months and
more. The great difficulty was to keep the larvae alive by obtaining water
almost daily from Adyar. Sea-water was tried, but the larvae did not thrive
in it. The diagrams given were made mostly from fresh material.
l'he #pawn-Masses.-These were found most abundantly during the summer
months. The first heavy rain swells the amount of water in these backwaters
and establishes a connection with the sea by opening up the usually closed
mouth of the Adyar. This enables practically all the water in these places
to empty itself into the sea. When this happens the spawn-masses are also
carried out to the sea by the force of the outgoing current. During the rainy
months the masses of spawn are but rarely seen. The masses are usually
pear-shaped, but cylindrical masses are not rare. Whatever the shape,
they are all provided with a long stalk which fixes them to the bottom, which
in these places is of some consistency, formed mainly of clay with a small
proportion of sand. I have never found them in purely sandy localities.
A great number of them get torn from their stalks and may be seen floating
on the surface of the water. When undisturbed and the wind light, as is very
often the case in the mornings, they float vertically after the manner of
miniature balloons, held in position by their stalks. Jelly-masses of recent
formation are perfectly traneparent, and the dark eggs may be seen shining
through the thick gelatinous mass. But most of the masses that one sees in
388
MR. R. OOPALA
AIYAR ON
these places are of a dirty colour, being invested by a covering consisting
mainly of soft ooze and organic debris adhering to the outside of the jelly,
forming a n envelope which no doubt affords an additional protection. Multitudes of diatoms and other small organisms may be found gliding on the surface,
but they do not seem to penetrate into the substance of the jelly. This may
perhaps be due to a thin pellicle surrounding the jelly.
The Stalk of the spawn-mass is formed of a much denser material than the
rest of it'; it is continued some distance into the middle of the mass in the
form of a dense core, round which the jelly is softer. The stalk is further
strengthened by pellets of faxal matter passed out by the adult worm.
During the months of March, April, and May (as usual in summer) the waterlevel in the Adyar and the M.V.G. backwater goes down considerably. On the
sides, the shore, in places for a yard or two, is covered with grass. On one
occasion there was heavy rain some miles west of Madras ; this water came
down the Adyar and by the evening of the next day the grassy sides of the
backwater were covered, but no spawn-masses were to be seen in the newly
submerged places. The next morning when I paid my usual visit to the place
I was surprised to find that an astonishingly large number of spawn-masses
had appeared overnight in the newly submerged banks. The dust-bins,
placed there by the military authorities to protect the sides of the sand-bank
running across the backwater, which were perfectly dry with heaps of rubbish
only, had also become partly submerged and inside them a few large spawnmasses had put in their appearance. The worms, which evidently had been
living beneath the soil near the edge of the water waiting for a, favourable
opportunity, had all come up during the night and had discharged their ova
along with the embedding jelly.
The same thing happened in another place also. Immediately south of the
Cemetery on the road to Adyar there is a marshy level plain which was mostly
dry. It is mainly covered during summer by Seuda mritima, and on the more
southern side by small shrubs of Avicennia with a little forest of aerial roots
round each. This marshy plain had also become submerged, and on the next
morning numerous pear-shaped masses of spawn were found scattered throughout
the plain and in among the roots of the Avicennia. Quite a different thing
happened in the portion of the Adyar above the Elphinstone bridge. Here
no spawn-masses had been formed. The water here had become greatly
freshened on account of the influx of rain-water and not even the slightest
trace of salinity could be detected, while the water in the M.V.G. backwater
had not freshened to the same extent on account of its proximity to the sea.
I have now observed the same thing occurring in other years also.
The above facts lead me to believe that the jelly-masses are formed at night,
that very little time, probably only a few hours, is taken in their formation,
and that the worm8, though capable of living in soil submerged under water
that is practically fresh, nevertheless discharge their ova only in water that
is distinctly saline. There is no doubt that the form itself is capable of living
A BEAOKISH-WATER POLYOEBTE WORM.
389
under water with a very low salinity for several months. It is suggested
(1) that the jelly affords protection to the cggs from the sun’s rays when the
tide runs out and leaves them exposed ; (2) that the jelly affords a safe place
of development during the initial developmental stages ; and (3) that it prevents
wide dispersal of larv-an
adaptation to backwater conditions.
Development.
Prototrochophore.-The eggs in the newly formed egg-masses are perfectly
spherical with it transparent membrane. Fertilization probably takes place
by the spermatozoa reaching the ova by penetrating the jelly. I n 24 to 36 hours
the spherical eggs which are 200p in diameter become uniformly ciliated,
and the ciliated embryos begin to revolve slowly in the jelly (text-fig. 1).
I
Fig. 1.-Uniformly ciliat,ed stage. x 360.
Fig. 2.--Very early metatroohophore. X 360.
Twenty-four hourv later, the spherical, uniformly ciliated embryos become
slightlyelongated, a little narrower in front than behind, with a uniform ciliation
except a t the front end where there is a tuft of fine cilia 39 to 4 times as long as
the othertl. The ordinary cilia are 1 4 p long, while the cilia of the apical tuft
are 54 p long (text-fig. 2). The body is mainly filled with greenish cells with
a few round globules a t the front end. The alimentary canal is not clear a t this
stage. The eyes have not become distinct. This stage evidently corresponds
to the Prototrochophore stage of Hacker (6). There is no trochophore stage
here, that stage being omitted from the life-history of the worm probably
on account of the development taking place in the jelly.
Initial Metatrochophore.-But the above stage is very transient, and soon the
uniform ciliation gives place to two bands of cilia. The first, a broad one,
stretches from the level of the eyes to about three-fifths the length of the body
from the anterior end. Behind the broad band there is a gap free from cilia
and about one-fourth the total length of the body in extent. This is followed
390
YR. R. O O P A U AIYAR ON
by the second band of cilia, the extent of which varies slightly, but usually
is half to two-thirds the breadth of the gap in front (text-fig. 3). This larva
answers to the description given for the initial condition of the Metatrochophore
stage of Hacker. The alimentary canal is distinct in this stage, is broad
in front and narrowed behind. No lateral tufts of a longer set of cilia are
discernible close to the posterior end of the front band of cilia. I n this respect
the larva of the present form differs from the Eunicid larva described by
Gravely (10). In the gap between the two bands of cilia on each side, an
invagination of the outer cuticle becomes observable. For a few hours
this invaghation appears, only to disappear again.
Late Metutrochophore.-A day later (i. e., 24 hours after the restriction
of the cilia to two ciliated bands) the invagination has become permanent,
Initial metatrochophorn with two bands of cilia, apical tuft,
and alimentary canal. X 350.
and projecting from the base of it may be seen an unjointed pointed sets.
This is soon followed by another, also unjointed, but differing slightly in shape
from the fist, being dilated a t the end and drawn out into a short point
(text-fig. 4). These two unjointed set= are always followed by a jointed
seta of the hooked vaziety (text-fig. 6). These three s e t s on each side constitute
the first pair of setose tufts. They are usually moved alternately, sometimes
withdrawn completely into their pits, sometimes protruded. The larva moves
with a screwing sort of rotatory motion, now and then seeming to contract and
expand its body. It requires 48-60 hours for the spherical, uniformly ciliated
embryos to become oval and acquire an apical tuft, two bands of cilia, and
a pair of parapodia. Thirty-six hours later after the appearance of the first
pair of parapodia the second pair of appendages appear in the form of a single
jointed seta on each side (text-fig. 6). The cilia still continue to be the loco.
motor organs, the larva swimming slowly in the substance of the jelly. The
A BRACKISR-WATER POLYUEETE WORM.
391
setose nppendages are only rarely brought into play, as when the larva leaves
the jelly and accidentally penetrates into the outer covering and so gets among
a group of diatoms. The alimentary canal a t this stage is sac-like, broad and
clear in front, and abruptly narrowed behind (text-fig. 5 ) . A t the front, end are
a number of transparent globules of some nutrient sustance. There is no trace
of jaw3 at, this stage. The larva measures 360 p long, 230 p broad, and
ohvioiisly corresponds to the late Metatrocliophore stage of Hacker.
One characteristic feature of this stage of development is that the first two
pairs of setose appendages always appear in the unciliated gap between the
two bands of cilia. In this respect the larva agrees with the Eunicid larva
figured hy Hacker (6) ; it differs, however, from the Eunicid Metatrochophore
4
Figs. 4 & 5.-TAate metatrochophores.
x 380.
larva figured by Gravely in his " Polychaete Larva " (10,pl. i, fig. 21), where
the setose tufts are shown as coming out of the region of the single broad
ciliated band and each tuft is said to consist of three compound seta. This
is not the case in this form.
At this stage, of the three set= of the first parapodia, the first formed is simple
and pointed, the second blunt and dilated a t the end, and the third is jointed.
The larva a t this stage does not exhibit that rotatory screwing movement
which characterized its earlier stages, swims more evenly, rotates only
occasionally, and uses its appendages more vigorously. The second pair of
appendages soon come t o consist of 3 s e t s on each side, all of them compound
and of the hooked variety (text-fig. 8).
392
M R . R. GOPALA A N A R ON
7
8
9
Fig. 6.-A single hooked compound seta. x ca. 2000.
Fig. ?'.-Late metatrochophore with three sotre in the first and one in the second tuft
A pair of anal styles present. x 350.
Fig. &-Still later stage with two pairs of setose tufts, each with three setm. Apical tuft
gone. x350.
Fig. 9.-Corresponding to early Nectochseta, with anterior constrictions. Cilia absent.
x 360.
A BRAUKISH-WATER POLYUH&TI WORM.
393
Nectochceta-Before the third pair of setose appendages are developed,
a pair of almovt globular, fleshy, transparent anal styles are formed a t the
posterior end (text-figs. 7 t 8). During this period the larva undergoes loss
of cilia, the apical tuft disappearing first, rapidly followed by the broad and the
narrow bandy of cilia. When the cilia are completely gone the pear-shaped
gelatinous mass gradually disintegrates, the non-ciliated larvae sink to the
bottom and commence their creeping mode of life.
10
Corresponding to a young Noctocheta. Specimen flattened nut
under pressure of coverslip. x 350.
A t the commencement of the creeping habit the body undergoes a slight
elongation and becomes twice as long as broad (text-fig. 9). I n front of the
first parapodial segment paired constrictions appear indicating segmentation
in this region. The larva then acquires a third pair of setose tufts, eaoh at b e t
394
MR, R. GOPALA AIYAR ON
consisting of a single seta, but later on of three s e t s all of which belong t o the
compound hooked variety (text-figs. 10 & 11). The first pair of chstigerous
appendages meanwhile develop a n additional compound seta on each side
and each tuft therefore consists of four setae, three of which may be jointed
and one always unjointed. The succeeding two pairs of tufts are always
provided with three compound sets.
This stage in the development of the present form is markedly different
from the corresponding stages of similar larvae already described. Gravely (9)in
Corresponding to a fully developed Nectochceta. Cilia absent. Rudiments of jaws,
three pairs of setme tuft,s, and two pairs of anal stJylesare present. x 350.
his “Studies on Polychaete Larvae,” says, “ I n the Nereidiformia and some other
worms there usually develop during the Metatrochophore stage a number
of segments, definite for each species, all of which appear a t about the same
time and whose parapodia become very fully developed before m y further
segments are added ; the former, including the peristomial and excluding the anal,
are called primary, the latter secondary segments.” I n the present form there
is no such precocious development of the appendages of any of the first-formed
segments, and consequently a distinction between primary and secondary
segments does not seem to exist.
A BRAUKISH-WATER POLYUEAZTEI WORM.
395
The alimentary canal becomes elongated ; it remains clear in the pharyngeal
region, in which a pair of chitinous toothed plates-the second maxilla-appear.
These are soon followed by the elongated mandibles, but the other parts of the
dental apparatus are not distinguishable as yet. A second pair of anal styles
external to those already present are developed a t this stage. The larva
(text-fig. 10) has now reached a stage corresponding to the Nectochaeta stage
of Hacker, who (6)describes it thus in his Pelagische Polychaetenlarven ” :
‘( Halbkugelformige Umbrella ; zweizeiliger Prototroch ; zwei Augenfleckpaare ;
zuniichst drei Paare Parapodien, bestehend aus einem grossen flossenformigen
ventralen Ast mit Borstenbundel und.ventra1 Cirrus, sowie aus einem dorsalen
Cirrus ; unpaare Scheitel-Cirrus, ein Paar Piihler-Cirren, zwei Paar After-Cirren.”
The description given and the diagram figured for the Nectochaeta of the
Naples species are very different from the corresponding stage in the present
form. I n Hacker’s form the three pairs of appendages have attained a considerable degree of specialization. There are oar-shaped fleshy parapodial
lobes from which bundles of jointed s e t s (6 in the first, 4 in the second, and
5 in the third) spring. Dorsal and ventral cirri, an unpaired apical cirrus,
a pair of dorsal tentacular cirri, and a pair of anal cirri are present. Two pairs
of eyes and two narrow ciliated bands are also present.
I n the corresponding stage of the present form, the setose parapodial tufts
start almost directly from the body, there being no basal flattened fleshy
processes. There are never more than three jointed s e t s in the second and third
pairs of tufts, and four s e t s in the first, of which one at least is always unjointed.
A single pair of eyes alone are present (almost black with a slight reddish tinge),
and as yet there is no indication of dorsal and ventral cirri. Cilia and ciliated
bands are completely absent. The larvae, unlike those of the Naples form, are
altogether incapable of swimming and remain creeping a t the bottom of the
glass. This is obviously an adaptation t o development in a jelly.
Prostomiurn, Eyes, and Cirri.-The prostomium is rounded, and does not
exhibit a t this stage that bifid condition which is so characteristic of the adult
Eunicid. The pharyngeal region remains clear, but the rest of the digestive
canal often exhibits a yellowish-green colour on account of the material in the
gut (text-fig. 12). The creeping habit is given up as new segments begin to
be added, and the tiny worms construct small tubes formed mainly of organic
debris cemented together by mucus secreted by the skin. New segments
are added in front of the anal segment, and the newly formed s e t s are usually
of the jointed variety. When 8-10 segments with their appendages have
been differentiated,the dorsal cirri make their appearance in the form of small
almost transparent fleshy tubercles. The ventral cirri appear later. The
larval eyes become gradually reduced, and when 13-14 chaetigerous segments
have been formed they are almost gone. Their place now is taken by the
adult eyes, which appear in the position afterwards occupied by the future
intermediate tentacles. At this stage the young worm is provided with two
pairs of eyes-the anterior pair gradually diminishing, the posterior gradually
becoming bigger.
DN. JOURN.-ZOOLOC+Y, VOL. XXXMI.
28
((
three
397
A BRAUKISH-WATER POLYCHlETE WORM.
8etce.-Meanwhile, the number of setae in the chaetigerous tufts of the anterior
segments has increased, and three kinds of setse may now be distinguished ;1. Unjointed capillary s e t s characteristically bent and taking up a more
and more dorsal position (text-fig. 13).
2. Jointed set= of the hooked variety with a short terminal hooked blade,
the basal shaft being slightly dilated and pointed a t the end (textfig. 14).
3. Jointed setae with moderately long sickle-shaped blade (text-fig. 15),
approximating to the falcigerous type. The second and third varieties
have a more ventral position than the first.
J,
\
14
I3
16
IS
20
Fig. 13.-A capillary seta of a worm with seven pairs of appendages. x 700.
Fig. 14.-A hooked aeta of the same worm. X 700.
Fig. 15.-Falcigorous scta of worm with 13 pairs of appendages. x 700.
Fig. l6.-A11 aciculum from the same worm. X 700.
Fig. 17.-An acicuiar seta, bent, with guard and hook, of the some worm. x 700.
Fig. 18.-A comb-seta from the posterior end of worm with more than 100 segments. x 700.
Fig. 19.-A capillary seta from the same worm. X 700.
Fig. 20.-A falcigerous seta from a worm with more than 100 segments. x 700.
Beside these, acicula (text-fig. 16) and acicular ‘setae (text-fig. 17) are
developed when the worm is provided with 12 to 14 pairs of appendages. The
former appear in the first few anterior Segments, the latter ctt about the same
?8*
398
MR. R. GOPALA
AIYAR ON
time in the posterior and are absent in the anterior segments. The combset% (text-fig. 18) also appear at about this time. In worms with 70-80 chaetigerous segments capillaryand falcigerous setm are found in the anterior segments,
while all three kinds of setm are represented in the posterior. The hind
segments still continue to form hooked and capillary setm. A t a fairly late
stage, in worms with more than 150 segments, the formation of hooked set%
in the newly-forming posterior segments is gradually given up ; only capillary
sets are developed in these. Thus worms of more than 150 segments have
capillary and falcigerous setm in the greater part of the body and only capillary
set= in the posterior segments.
An examination of the parapodia of very young worms of different ages
shows a series of transition-stages. The text-figs 21-29 show clearly the facts
set forth above.
F
I
2
J
Fig. 21.-lst
Fig. 22.-1st
Fig. 23.--6th
Fig. 24.-16th
23
24
right parapodium of a worm with 7 pairs of appendages. x 360.
left parapodium of a worm with 16 pairs of appendages. x 360.
right parapodium of the same worm. x 360.
right parapodium of the same worm. x 176.
Text-fig. 21, the right setose tuft of a worm with seven pairs of appendages,
shows three jointed setm of the hooked variety, one capillary seta, and no
set= of the falcigerous kind.
.
Text-figs. 22 and 23 show the 1st left paripodium and the 6th right parapodium of a worm with 16 pairs of tufts, both providedwith dorsal cirrus,
rtciculum,and sets of all the types ; while text-fig. 24shows the right parapodium
of the 15th chstigerous segment, without dorsal cirrus and miaulum, but possessing an acicular seta with guard and three jointed setm of the hooked variety.
A BltACBISH-WATER POLYCHETE WORM.
r
399
26
Figs. 25 &, 26.-The first and fifth parapodia of a worm with 26 pairs of parapodia and there
tentacles. x 175.
Figs. 27 & 28.-The f i s t and fifth parapodia of a worm with 80 setigerous segments. x 176.
Fig. 29.-A right parapodium from the posterior end ofa wormwithabout 176 chsetigerous
segments. x176.
(Figs. 21-29 from dorsal aspect under coverslip.)
400
M R . R. QOPALA AIYAR ON
In text-figs. 26 and 26, representing the right parapodium of chatigerous
segments 1 and 5 of a worm with 25 pairs of appendages, all three kinds of
seta are seen to be present.
I n text-figs. 27 and 28, which represent the parapodia of chatigerous segmentd
1 and 5 of a a worm with more than 60 pairs of appendages, all the hooked
s e t s have been replaced by sickle-shaped ones. Text-fig. 29, a parapodium
from the extreme posterior end of a worm with more than 150 segments, shows
no jointed seta at all.
The h a 1 condition of the seta is thus arrived at rather late, and it becomes
a question of how far descriptions of setm based on the examination of small
worms can be of specific value.
Dental apparatus of young worm with 26 pairs of appendages. A. Forceps jaw;
B. 2nd maxilla ; C. 3rd maxilla ; D. 4th maxilla ; E. 8th maxilla ; F. Additional
plate ; G . Mandible. X 40.
Jaw8 begin to appear as early a8 the Stage which corresponds to the Necto.
chat&,and the full complement of parts is reached by the time that 8-10 pairs
of appendages have been formed. When fully formed the entire jaw appara,tus
consists of the following (text-fig. 30) :1. A pair of ventrally placed mandibles, long, slender, and diverging
posteriorly, broad and united anteriorly, with three big obtuse teeth,
A BRACKISH-WATER POLYCHBTE WORM.
401
2. A pair of forceps jaws, each of two pieces, the basal pieces united by the
greater part of their length and black behind. The distal pieces
are robust, bluntly pointed, moderately curved, and black at the tips.
No teeth are present. The proximal pieces are cut off obliquely
a t their bases, ao that a notch is formed between the two apposed
pieces at the posterior end.
3. The second pair of maxillae (grinders) are massive and provided with
five black teeth on the left and six on the right side.
4. The third pair of maxillae are in the form of crescentic plates, the right
being the bigger and placed slightly in advance of that on the left
side, both being marked by a ridge and elevated into 8-9 small
tubercles on the right and 5-6 bigger ones on the left.
Anterior end of a worm with 60 setigeroua segments, three tentacles, and a pair of eyes.
Only capilIary and faloigeroua set= are present in the anterior segments. x 40.
(All drawing6 made from fresh preparationa.)
The number of teeth in the second and third pairs of maxillae is subject
to great variation. They are more numerous in the younger than in the adult
stages.
5. The fourth pair of maxilla? are irregular with four indistinct teeth
on each, the teeth on the right side being much less conspicuous than
those on the left.
6. The mth pair of maxilla are in the form of rhomboidal plates elevated
all T C U into
~ ~ a ridge. Teeth are absent.
402
MR. R. OOPALA AIYAR ON
On the left side there is in addition another piece, toothless and unrepresented
on the right side.
Gills arise in worms with 15-16 pairs of appendages as single filaments from
the dorsal cirrus of the 8th or 9th pedigerous segment. The full number of
filaments and pectinate shape are attained gradually as more segments are added.
Tentacles.-The median tentacle appears for the first time when the worm
ia provided with 18-20 segments, grows rapidly, and two days later is followed
by the intermediate tentacles. The lateral tentacles develop very late, only
when more than 80 pairs of appendages have been formed.
This late development of the tentacles is in marked contrast with their
early development in the Nectochsta of the Naples species and other Nectochseta larvae described by Gravely for other families of the Nereidiformia.
The worms reared in the laboratory from the spawn-masses are exactly
like the worms dug out from the soil where the pear-shaped masses of spawn
abound, except in their smaller size and in the smaller number of filaments
in each gill. It takes nearly six months for a worm to develop 150 to 180
segments and the gills to acquire 5-6 filaments. Judging from this the worms
dug out from their natural habitat, sometimes measuring up to 18 inches or morc
and possessing about 750 segments, are probably 3-4 years old a t the least.
Borradaile (7) describes the initial development of a species of Marphysa
(teretiuscula 2) with which the development of the present form very closely
agrees. His account, however, extends only up to the formation of the fourth
setiger, and the few minor differences are what one would expect in two different
species of the same genus. Dr. Southern* mentions similar spawn-masses
as being formed by M . gravelyi from the Chilka Lake and figures a n early stage
(12))Herpin (16)traces the development of Eunice harassii to a much later
stage, and a comparison of the development of present form with that of
E . harassii is highly instructive.
I n E . harassii the eggs are not laid in a jelly, and this seems to be the reason
for the many differences in the details of development. Here there is a wellmarked pelagic phase lasting for over ten days, during which the larva seems
to be engaged in parapodial differentiation rather than in the quick formation
of new setigers. At the close of the pelagic phase the fourth setiger has appeared
and the first already possesses a dorsal and a ventral C ~ R
and, by the twelfth
day the second is also equipped in a similar manner. The larva passes in
succession through what Herpin calls the (‘Nematonereis,” ‘(Lysidice,”
and “ Amphiro ” stages, characterized respectively by (i) a median tentacle,
(ii) median and intermediate tentacles and absence of branchiae, ( 5 )median and
intermediate tentacles and simple branchiae with absence of pectinate set*.
Development is very slow, being characterized by rapid differentiation of
existing parts rather than by the addition of new setigers. Thus a t the
&matonereis stage, which is reached in fourteen days there, is a median
* me Madras form was submitted to Dr. Southern, and he considor8 it to be different
from M.grccuclyi.
A BRAUKISH-WATER POLYUHETE WORM.
403
tentacle and five setigers only. The Lysidice stage is reached in three months
and the larva is provided with three tentacles and 13 setigers, and at the
Amphiro stage, which takes ten months to reach, 3 tentacles, 20 setigers, and
eimple branchize have appeared.
From what has been said it will be seen that it is not possible t o apply the
terms Nematonereis, Lysidice, and Amphiro to the stages of development
of the present form, for here we have in the course of development t i curious
overlapping of characters and an absence of that orderly process so characteristic of E . harassii.
Unlike Staurocephalus, the definitive pair of eyes, as in E . harassii, are the
posterior ones.
BIBLIOGRAPHY.
1. AGAYYU,
A. Young Stages of a few Annelids. Ann. Mag. Nat. Hist. ( 3 ) xix, 1867.
2. CLAPAR~::DE,
E. AnnOlidos Chdtopodes du Golfe de Naples. 1868.
3. M‘INTOYH,W. C. Early Stages in the Development of P?iyZZodoce wmculato. Ann.
Mag. Nat. Hist. ( 4 ) iv, 1869.
4. FEWKEY,
J. W. On tho Development of somo Worm Larvse. Bull. Mus. Comp. 55001.
Harvard Coll., Camb., Mass. xi, 1883-85.
5. DE SAINT, JOSEPH.
A i d l i d e s Polychbtes des cStes de Dinard.
Ann. Sc. Nat. Zool.
vii, 1886.
6. HACEER,
V. Pelagische Polychiitenlarven. Zeitschr. wiss. Zool. lxii, 1897.
7. BORRADAILE,
L. A. On the Spawn and Young of a Polychsetc Worm of the Genus
0
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