CHIROCEPHALUS. 
49 
also says that they are incapable of bearing any degree of 
cold. Jurine, however, found no difficulty in hatching 
the ova of the Chirocephalus sent to him by Prevost, and 
keeping the animals so hatched till they reached maturity ; 
and Shaw distinctly asserts that he has found them in 
this country in shallow pools, in the months of December 
and January, even after pretty sharp frosts, as lively 
almost as in spring or summer. I have always found 
them in the months of October, November, and December, 
and even after frosts of short continuance, though of con- 
siderable severity. In general they have been very short- 
lived after being removed from their native habitat, but I 
have been able to hatch the young and watch their 
progress to maturity. Though they do not appear de- 
structive to other animals, they fall an easy prey them- 
selves to various enemies. Progs, salamanders, the larvae 
of the Dytisci, the Cyprides, and other such inhabitants 
of the water, kill them in vast numbers, and they seem, 
besides, according to Prevost, to be specially infested by 
a species of Vorticella, or wheel animalcule, which attaches 
itself to the body of the animal in great numbers, and 
wmdd very soon, were it not for their moulting frequently, 
completely destroy it. I have found them very liable to a 
peculiar disease, which seems very frequently to terminate 
fatally. It attacks their body near the external ovary, the 
lower part of the abdomen, &c., and the branchial feet 
are not exempt from it. It consists of a white growth, 
composed of a fatty sort of substance, and when once 
this appears, the poor animal almost always soon after dies. 
When copulation takes place, the male glides under- 
neath the female, and seizing her firmly with his 
powerful prehensile antennse, forces her to bend her 
tail towards his abdomen, where the male organs lie. 
The ova appear at first as small, white, spherical bodies 
lying in the internal ovary, which stretches along the 
abdomen, and then passing from it into the external 
ovary already described. When the proper time arrives, 
the mother deposits these ova loose in the water, the 
4 
