History of British Entomostraca. 523 



perfect insect, though varying a little in the shape of the shell ( Fig. 1 2). 

 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 beingin 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 

 setee of the antennae, &c. 



The food of these little insects consists of dead animal matter and 

 confervee, &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. m m 



