34 THE LIVER-FLUKE 



has an outer structureless cuticle, a thin muscular 

 layer, and an epithelial layer lining the cavity. 



The eye-spots, though losing their form, persist ; 

 and ciliated excretory funnels are present. Such 

 sporocysts sometimes, though rarely, multiply by 

 transverse fission in the early stages of their develop- 

 ment. 



B. The Second Generation consists of redise, which are pro- 

 duced asexually within the sporocyst, and are themselves 

 asexual. 



1. From the epithelium of the sporocyst, cells are budded off, 



which segment to form solid masses or morulae lying 

 in the cavity of the sporocyst. Each of these be- 

 comes flattened on one side, and then invaginated 

 to form a gastrula : this increases in size, elongates, 

 and develops into a redia. The rediae so formed 

 force their way out of the sporocyst and become 

 free : the wound in the sporocyst heals, and other 

 redias are formed in the same way within it. 



2. The free redise wander about in the snail, increasing in 



size and being especially abundant in the liver. The 

 adult redia (fig. 11) is a cylindrical body about 1-5 

 mm. long, with a collar-like ridge running round it 

 near the anterior end, and with a pair of blunt pro- 

 cesses projecting from the hinder part of the ventral 

 surface, which aid in locomotion. The body-wall 

 resembles that of the sporocyst in structure, but is 

 more muscular, and has definite excretory canals 

 which commence as funnels with ' flame-shaped ' cilia. 



The alimentary tract is a comparatively short 

 blind sac, with walls one cell thick : the mouth is 

 at the anterior end, and behind it the wall of the sac 

 is thickened to form a strong muscular pharynx. 



From the inner surface of the body-wall of the 

 redia, cells are budded off which develop into gastrulaa 

 as in the sporocyst : of these some become rediae like 

 the parent, while others develop into cercariae. 



