Marshall—A Parasitic Ostracod. 
121 
nal parts, and in, specimens that have been cleaned and 
mounted, the removal of the shell aids but little in, working out 
the internal organization. 
There is a slight variation in the shell of different individ¬ 
uals, also between the different sexes. In PI. XI, figs. 11 and 
12 are figured three male and four female shells, all drawn to 
the sarnie scale. It will be noticed that the youngest male shell 
is very similar to all three of the youngest females. When, 
however, the animals become older the anterior end shows a 
tendency to become pointed, a characteristic much more notice- 
able in the male than in the female. Again in the male the 
comparative height is not at any part so great, and it lacks the 
rounded edge present in the female. 
In the shell duplicature, PI. XII, fig. 19, very nearly the 
same structure is shown as figured by Claus. Taf. XII fig. 9, 
for Pachycypris Leuclcarti. At either side the layer of hypo- 
dermjal cells is present, those on the outer layer being larger 
than the inner ones. The nuclei are small and scattered regu¬ 
larly but not so close together as figured by Claus. Connecting 
the two sides were a, number of supporting fibres differing iu 
structure from the hypodermal cells. They stain readily but 
appear nearly homogeneous. The peculiar sub-hypodermal cells 
which appear so numerous in the figure already cited from 
Claus, are abundant, in Entocythere only in the anterior parti. 
They stain very darkly and are especially noticeable in the great 
number' of vacuoles they contain. 
First antenna :—The insertion of the first antenna is directly 
under the posterior margin of the eye. Its basal segment PL 
X, fig. 1, is; much, larger than any of the others, possessing 
two muscles which from their position, one dorsal and one ven¬ 
tral, appear to be used as extensor and flexor of the rest of the 
antenna. The proximal part of this segmlent is encircled by a 
chitinous ring-like band from which the muscles arise. The 
other five segments are very similar in shape, differing in the 
number of setae and in the size which decreases' toward the dis¬ 
tal end. The second segment has two small muscles which oc¬ 
cupy in it the same positions that the muscles did in the first 
segment. In the four last segments nothing that could be dis- 
