99 
in detail (fig. 2). They each form a slender tube extending through the exposed 
part of the trunk in close juxtaposition to the intestine. At the anterior extre¬ 
mity, which, unlike what is often the case with the ovaries, never penetrates the 
part of the body-cavity covered by the carapace, 4 small ccecal lobes are seen 
outside. These lobes, in the genus Leucon (figs. 2, 3), are very short and 
somewhat unequal in size, whereas in Diastylis (figs. 12, 13) they are more 
prominent, almost digitiform, and of about equal size. They contain the germinal 
stratum of cells, from which the zoosperms are developed, the tube itself being 
filled with densely crowded bundles of fully develojDed zoosperms, whereby it 
acquires a closely striated appearance. Behind, each tube contracts to a narrow 
duct, which in the last pedigerous segment curves abruptly downwards, debouching 
on the ventral face of the latter at the tip of 2 small juxtaposed prominences 
(see fig. 2). The zoosperms are of considerable size and arranged in dense 
bundles, each bundle being developed from a single germinal cell and containing 
about a dozen zoosperms. At first the bundle is enveloped by a thin membrane 
(see fig. 4); but this soon becomes ruptured. The zoosperms, however, still 
remain tied together in bundles (see fig. 5), and it is only after being evacuated 
from the body that they separate. Each zoosperm (see figs. 7—11, 14 — 16, 
22 ) consists of 2 unequal parts uniting at an acute angle. The smaller part is 
of very delicate structure, and exhibits traces of a nucleus at its base. It varies 
somewhat in form in different Cumacea, being sometimes lanceolate in shape 
(figs. 9 — 11), sometimes more thread-like (figs. 7—8, 14—16), and in some cases 
distinctly twisted (fig. 22). When not fully developed, this part is curled up in 
a close coil, as found in young male specimens of Diastylis (figs. 17 — 20). It 
seems to represent the essential part of the zoosperm, answering to the so-called 
head in zoosperms of the usual form. The larger part of the zoosperm, answering 
to the tail, has the form of a slender elastic seta, several times as long as the 
above-mentioned part, and terminating in a very fine point. 
