30 



STUDIES IN ANIMAL LIFE. 



Having managed to get into the body of the water- 

 snail, the animalcule's part in the drama is at an 

 end. It dies, and in dying liberates the sac, which 

 is very comfortably housed and fed 

 by the snail. If you examine this sac 

 (Fig. 5), you will observe that it has 

 a mouth and digestive tube, and is, 

 therefore, very far from being, what its 

 name imports, a mere receptacle ; it is 

 an independent animal, and lives an 

 independent life. It feeds generously 



Fig. 5. CEBCABIA , . . , ., -, , 



SAC. on the juices of the snail, and, -having 

 fed, thinks generously of the coming 

 generations. It was born inside the 

 different Stages animalcule ; why should it not in turn 

 give birth to children of its own ? To 

 found a dynasty, to scatter progeny over the boun- 

 teous earth, is a worthy ambition. The mysterious 

 agency of reproduction begins in 

 this sac-animal, and in a short 

 while a brood of Cercarice move 

 within it. The sac bursts, and 

 the brood escapes. But how is 

 this? The children are by no 

 means the " very image" of their 

 parent. They are not sacs, nor 

 in the least resembling sacs, as 

 you see (Fig. 6). 



They have tails, and suckers, 

 and sharp boring instruments, 



Fig. 6. CERCABIA DEVEL- 

 OPED. 



A, mouth; B, B, B, excre- 

 tory organ; C, pigment 

 spots ; D, tail. 



