242 PARASITIC HABITS OF CRUSTACEA. 
find these or similar parasites. The male lives free in the 
visceral cavity, but the female is much larger and stationary, 
and as the ovaries develop, the clusters of eggs and tip of 
the abdomen project through the integuments of its victim. 
Another Entomostracan genus; Doridicola, contains small 
active species which are external parasites on the gills of 
similar mollusca 
The Tetradecapods are not so often parasitic as the Ento- 
mostraca, yet many curious parasites of fishes, etc., belong 
to this division. The Isopod order, including the pill-bugs, 
and many aquatic species having a similar depressed form, 
contains more parasitic species than does the Amphipod 
order, which includes the compressed species. 
Among the parasitic Isopods we find some curious species 
which live parasitically in the mouth of fishes, usually ad- 
hering firmly to the roof of the mouth by means of their 
numerous strong and sharp claws, and in that situation often 
grow so large as to almost entirely fill the mouth, causing 
no doubt a great amount of suffering to the helpless fish, 
and, perhaps, eventually its death by starvation. Such are 
the habits of certain species of Livoneca and allied genera, 
while other similar species live upon the exterior and in the 
gill-cavity, both of marine and fresh-water fishes. I have 
recently found an allied form in the stomach of a toad-fish 
from Florida, where it appeared to be truly parasitic. It 
was nearly an inch long and half as wide. Nerocila, Anilo- 
era, and Cymothoa, are allied genera, including numerous 
species, all of which are parasitic on or in fishes. These 
genera have a more or less, oval or oblong, broad, stout, 
depressed body, with short crooked legs housib, armed 
with sharp claws. Some of these species become three 
inches long and nearly an inch broad, and must be very 
annoying. 
. Another related group of Isopods includes Bopyrus and 
= with allied genera, which are parasitic on other Crus- 
a oe aro a, and have the ordinary 



