THE SEGMENTAL EXORETORY ORGANS O F CRIJSTACEA,
467
Notes on the Segmental Excretory Organs of Crustacea.-V. On the Maxillary
Glands of the Syncarida. By S. M. MANTON,M . A . , Ph.D., F.L.S., Demonstrator in Comparative Anatomy in the University of Cambridge and
Fellow of Girton College.
(With 2 Text-figures.)
[Reed 6th Maroh, 1930.1
AMONGthe Syncarida the maxillary glands of Anaspides and Bathynella have
already been described (Cannon and Manton, 1927 ; Chappuis, 1915). The
diagrammatic reconstruction of the gland of Anaspides (Cannon and Manton,
fig, 2, p. 443) was made from slightly oblique sections of uncertain thickness,
and was intended merely to show the main pattern of the duct-looping for
comparison with that of Chirocephalus. Fresh materal was obtained on a visit
to Tasmania during 1929, and detailed reconstructions of the maxillary glands
of Anaspides, Paranaspides, and Koonunga have been made.
The general disposition of the coils of the efferent duct of the maxillary
gland in Paranaspides, Anaspides, and Koonunga is similar. Owing to the
coils being in all cases considerably superimposed, parts of the ducts are drawn
separately in text-fig. 1 a, c & e, while the deeper coils and end-sac are shown
in text-fig. 1 b , d & f. The efferent duct shows two homologous loops, X and Z,
lying in the upper anterior part of the gland. The points X and Z are connected
by a loop passing through the point Y, while from X the duct passes to the
end-sac and from Z to the exit on the maxilla (text-fig. 2).
The details of the coils of the gland may now be considered. The duct
from its opening on the maxilla runs upwards and forwards forming a n S-shaped
bend-(P in text-fig. 2)-in all three animals, but in Koonunga this bend is
very much smaller than it is in Paranaspides and Anuspides. The duct then
passes upwards to the bend Z, forming an angle K on the way. The bend K is
most fully developed in Koonunga. From Z the duct loops downwards to the
point Y and upwards to X. In Paranaspidea the loop to Y is very long, in
Anaspides it is shorter and in Koonunga it is hardly formed a t all. From
x the duct reaches the end-sac in Paranaspides by way of a simple S-shaped
twist. In Anaspides and Koonunga the middle part of the S-shaped loop has
been folded so that the duct crosses over itself a t A before reaching the endsac. The position of this folding, however, is not quite the same in the two.
I n Koonunga it has been caused by an outward and backward fold of the
duct, while in Anaspides the folding has been inwards and forwards. The duct
in Paranaspides is fenestrated and presents several blind projections, mainly
TEXT-ma.1 (Amt part).
IEecomtruotions of the maxillary glands of Paranaapides, Anaspidea, tmd Koonunga.
The exit tube and mpfficial coils of the duot am shown in figum a, a, end 6, while
the deeper c o b of the duct are shown in figures b, d, mdf, the thin lines representing
the positions of t4e superficid coih. o a . , e n d - w ; p., opening between end-wc
and duot ; K, X, Y, and Z, homologous points on the ducts.
TEXT-PIG.
1 (second part)
K
2
[For legend, eee prev~ouepage ]
470
DR. 8. M,MILNTON ON TEE
'Jhm-~la.
1 (third part).
Y
[For Ingend, me p. 468.1
SaOMlDNTAL EXORETORY ORGANS OF URUSTACEA.
TEXT-FIQ.
2.
f
ANASPIDES
PAR A N AS P IDES
KOONUNGA
Diagrams showing the plan of the looping of the ducts of the maxillary
glands of Paranaspidea, Anaspidea, and Koonunga.
471
472
THE SEGMENTAL PlXCRETORY ORQANS OF 0RUSTAU.U.
located near the end-sac and near the exit (text-fig. 1 b). In Anaspides a single
fenestration is present through the duct near the end-sac (text-fig. 1 d ) .
These fenestrations resemble those found through the end-sac in certain Branchiopoda.
The end-sacs of Parampides and Ampidee are relatively larger than that
of Koonunga, and communicate with the duct by a simple opening which is
very large in Parampides. The cells bounding this opening in Paranaspides
are swollen and project into the lumen much as do the ‘‘ valve ” cells of
Anaspides already described (Cannon and Manton, 1927), but the large size of
the opening between end-sac and duct in Parampides precludes these cells
from exercising a valvular function unless the region is very contractile.
No muscle-fibrils could be detected around the opening. The fixation of
Koonunga did not allow of a detailed examination of the junction of the end-sac
and duct.
A comparison of the maxillary glands of Parampides, Anaspidea, and
Koonunga shows a close resemblance between Parampides and Anaspides
in the positions of the duct and end-sac. Loops P and Y are well formed in
both, and the end-sac is of a similar shape. Loop Y shows progressive
reduction passing from Paranaspides to A m p i p e s and Koonunga. The ducts
of Anaspides and Koonunga, however, resemble each other in possessing a
loop A. This loop has not been formed in the same manner in the two
animals and was probably independently acquired from some form without
this loop. The pattern of duct shown by Anaspides and Koonunga could
have been derived from a type resembling that of Paranaspides in general
form, but lacking its peculiar features of excessive duct fenestration, and
perhaps, the extended loop Y. Such a conception of the inter-relationships
of the glands in the three types is in harmony with conclusions on the
affinities of the three animals based upon external anatomy and habits.
REFERENUES.
CANNON, H. O.,& MANTON, S. M. 1927. Notes on the Segmental Excretory Organs
of Crustaoea. 1 & 2. Journ. Linn. SOC.London (Zool.), vol. xxxvi, pp. 439-456,
with 7 text-figs.
CHAPPUIS, P. A. 1916. Bathynella: natans und ihre Stellung im System. Zool. Jahrb.,
Abth. Syst. vol. xl, pp. 147-176, with 17 text-figures.