THE FIGURES. 125 



sumed that those creatures which are produced from 

 the ova of the Distoma in the common embryonic 

 form of the Distomata {comipare fig. 1 h) — the first 

 generation — are of an allied nature. Figs. 2 d and 

 2 c are individuals, in which is a new progeny in 

 the form of globular germs, and which occupies 

 only the posterior part of the body ; 2 h and 2 a 

 show partly developed embryos, filling nearly the 

 whole cavity of the body. 



Figs. 3-4. The second generation in the development of 

 the Distoma. {The " nurses," am7ne.) 



Fig. 3. A series of forms, through which the young 

 pass from the globular germs in the "parent- 

 nurses" figs. 3 a — d ; during their growth they be- 

 come at first oval, figs. 3 e — g ; but afterwards more 

 elongated, and almost cylindrical (Ji i k I,) whilst a 

 small process which is situated at one end is length- 

 ened into a sort of tail, and a depression at the op- 

 posite extremity is formed into a mouth and oral 

 cavity. Figs, tmno p, are older embryos, which 

 exhibit the parts named above more distinctly; a 

 pair of lateral processes at the root of the tail, as 

 also a depression below the head, become more 

 e^ädent ; the interior large cavity represented at v is 

 a digestive sac. Figs. 3 o and jo are fully developed 

 individuals (" nurses") in which the germs of another 

 generation (the third) are distinguishable just above 

 the root of the tail. 



Fig. 4. The growth of the second generation, the 

 " nurses" {amme) and the hatching or incubation of 

 the third generation {the Bistoma-larvcje). 4 ^ is 

 very young, and has recently quitted its "nurse" 

 — the "parent-nurse" {grossamme) ; 4 c is half- grown, 

 and the germs of the third generation contained in 

 it are partly developed into embryos, and show that 



