80 



STUDIES IN ANIMAL LIFE. 



Having managed to get into tlie body of the water- 

 snail, tlie 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 

 on the juices^ of the snail, and, having 

 fed, thinks generously of the coming 



Fig. 5. — Ceeoaeia 

 Sao. 



A, mouth; B, di- 

 gestive tube; C, 

 a cerearia newly . • -r, i • • i j_i 



formed: four oth- generations, it was born mside the 



ers are seen in 

 different stages 

 — magnified. 



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 (Pig. 6). 



They have tails, and suckers, 

 and sharp boring instruments, 



Fig. 6. — Ceeoaeia dsvel- 



OPED. 



A, moutli; B, B, B, excre- 

 tory organ; C, pigment 

 spots ; D, tail. 



