History of British Entomostraca. 523 
perfect in sect, though varying a little in the shape of the shell (Fig. 12). 
According to Jurine they undergo several moultings before they are 
fit to procreate their species the frequency of these moultings depend- 
ing upon the season of the year, and being in proportion to the gradual 
development of the insect. Moulting continues to take place in the 
adult after each laying and as the shells of these little animals be- 
come very frequently perfectly covered with dirt and moss, which 
adhere close to them, this change of covering becomes a useful act 
to disembarrass the insect of a shell become disagreeable to it ; 
while, in the young, their development can only take place by get- 
ting rid of the shell as soon as it becomes too small for the body 
contained within. This renewing of the shell forms a fine example 
of the process of exuviation, as naturalists call it the change 
which takes place being most complete, for not only does the shell 
itself fall off, but the insect casts off even the external parts of the 
body, the fine pectiniform branchiae and minutest hairs clothing the 
setae of the antennae, &c. 
The food of these little insects consists of dead animal matter and 
confervae, &c. Straus says, he never saw them attack living animals 
when these were well and strong, but he has frequently seen them 
attack worms, &c. when wounded and weak. Though dead ani- 
mal-matter is their choice, they will not, he adds, eat it when pu- 
trid. They, no doubt, also prey on each other, as I have frequently 
seen individuals of one species devouring eagerly the dead carcasses 
of a species different from themselves. 
When the ponds and ditches in which they live dry up in sum- 
mer, they bury themselves in the mud, and thus preserve their lives 
as long as the mud retains any moisture becoming active as ever 
when the rain falls and again overflows their habitations. After 
long continued droughts, however, when the mud becomes very dry and 
hard, they perish ; but, as Straus observes, the eggs will not perish 
along with the parents, but will be hatched four or five days after be- 
ing placed in water. I have given, in my paper on the Cyclops, the 
result of Jurine's experiments upon the power these insects have of 
resisting drought ; but, though it appears from what is there stated 
that they will not stand drying quite, yet I have no doubt, from 
what I have observed in summer, that the Cyclops can prolong their 
existence also by plunging themselves in the mud for, when ex- 
amining ponds which had been filled again by the rain, after re- 
maining two months dry, I have found numerous specimens of the 
C. quadricornis in all stages of growth. 
These little creatures seem to be very lively in their native ele- 
NO. vi. Mm 
