150 HKLTISH ENTOMOSTKAi \. 



in a place of security, that it cannot be displaced by any 

 agitation of the water, and is occupied twelve hours in 

 the operation. The eggs remain about four days and a 

 half before they are hatched, and then the young at once 

 assume the appearance of the perfect animal, though 

 varying a little in shape of shell. According to J urine 

 they undergo several moultings before they arc fit to pro- 

 create their species ; the frequency of these moultings 

 depending upon the season of the year, and being in 

 proportion to the gradual development of the animal. 

 Moulting continues to take place in the adult after each 

 laying, and as the shells of these little animals get very 

 frequently covered with dirt and moss, which adhere close 

 to them, this change of covering becomes a useful act to 

 disembarrass the animal of a shell now disagreeable to it ; 

 while in the young, their development can only take place 

 by getting rid of the shell as soon as it becomes too small 

 for the body contained within. The renewing of the 

 shell forms a fine example of the process of exuviation, as 

 naturalists term it. The change which takes place being 

 most complete ; for not only does the shell itself fall off, 

 but the animal even casts off the internal parts of the 

 body, the fine pectiniform branchhe, and the minutest 

 hairs clothing the seta; of the antenna 1 , &c. 



The food of these little creatures consists of dead animal 

 matter, Conferva:', &c. Straus says he never saw them 

 attack living animals when they werewell and strong, but he 

 has frequently seen them attack worms, &C., when wounded 

 and weak. Though dead animal matter was their choice, 

 they will not, he adds, eat it when putrid. They no doubt 

 also prey on each other, as 1 have often observed indivi- 

 duals of one species devouring eagerly the dead carcases 

 ol'speeies diHerent from themselves. When the ponds and 

 ditches in which they live, dry up in summer, they bury 

 themselves in the mud, and thus preserve their lives as 

 long as the mud retains any moisture, becoming active as 

 ever \\lien the rain falls and again overllous their habita- 

 tions. After Long-continued drought, houever, when the 



