242 GIGLIOLI, ON THE GENUS CALLIDINA. 
A, vulgaris, which frequent the roots and under leaves of 
aquatic plants, exists necessarily in darkness. I do not 
know, however, if they perish when exposed to the light, 
not having made the experiment. 
Reproductive organs.—As yet I have not met with a single 
male individual of this species; that is, I have not seen any 
not provided with an alimentary canal. I have observed 
many small ones without ovaries, but they were, doubtless, 
young. This is remarkable, considering the large number I 
have examined. The females have one or two ovaries, the 
latter number being the commonest; they are large, irregu- 
lar, oval bodies, situated one on each side of the digestive 
apparatus (figs. 1, 2), and consisting of a finely granular 
mass, in which may be seen, more or less distinctly, germinal 
vesicles and spots (fig. 9). The length of an ovary I mea- 
sured was ;~6,ths of an inch, and its breadth -2,,ths of an 
inch. I could make out no distinct oviduct. An ovum, 
which could not have been long laid, measured -_3,,ths of an 
inch in its long diameter, and +2,,ths of an inch in its short 
one (fig. 6). The ova, when deposited, adhere, by their 
posterior and smaller extremity (where the posterior part of 
the embryo’s body is afterwards developed), to the appendages 
of the crustacean on which the mother lives (fig. 7). 
Development takes place very soon; the egg, after the 
blastoderm is formed, assumes a somewhat pear-shaped form, 
Tn the largest ovum (fig. 7) the embryo is quite formed, the 
trochal disc is entire, and the ciliary action was going on 
most vigorously when I observed it; the mastax is distinct, 
and part of the alimentary canal can readily be made out. 
The length of the mature egg is 7% ths of an inch; the 
breadth, —2,,ths of an inch. The enclosed embryo was 
—*,ths of an inch in length. 
I found nothing corresponding to ephippial ova. 
In the neck and tail exist a number of what old authors 
thought to be glands, and which were very properly termed 
by Professor Huxley vacuolar thickenings. 
