THE FIGURES. 129 



Figs. 2-6. The last {third ?) generation of the Distoma. 

 Embryos, Larva, Pu/pa, Bistomata. 



Fig. 2. The successive forms of tlie development of the 

 germs into embryos ; the T)istoma-larv(2 correspond 

 wholly Avith the forms given in Plate II, figs. 5. 

 The spiciüum on the anterior part of the head is at 

 last distinguishable. 



Fig. 8. Bistoma-larvcs or Cercarice. {Cercaria armata, 

 Siebold,) after they have quitted the " nurses" and 

 snails and are swimming about in the water ; 3 b 

 and 3 d, individuals with contracted bodies, moving 

 on a flat surface ; 3 e, a lateral view. 



Fig. 4. Distoma-piipa. 4 ß, a portion of the integu- 

 ment of the snail, closely beset with the oval Dis- 

 toma larvcs, in the pupa state; slightly magnified. 

 4 (5, a Distoma larva, on the point of forming its 

 mucoid case. 4 c, a larva recently become a pupa, 

 the abdomen of which is turned upwards ; (ro'" 

 long, .ffo'" broad). 4 d and 4 e, rather older ptipcB ; 

 4if and 4 ff, pupcs, the animals of which are ready to 

 quit the pupa case. The organs marked s — ö are 

 the same in all the figures as in fig. 5 ; s, the ori- 

 fice of the excretory organ; t, the borders of the pos- 

 terior body surrounding the root of the tail, which 

 form a horse-shoe shaped acetabulum ; u, the abdo- 

 minal sucker ; v, a pore situated between the sucker 

 and the posterior border of the body, which in 

 figs. 4/ and 4y appears to be connected with the 

 sei-pentine organs x x ; y, the excretory organ ; ce, the 

 oral orifice ; ö, the cast off frontal spiculum. 



Fig. 5. The animals produced from the pupae, true 

 Disfomata, Distoma tarda ; 5 a, an individual re- 

 cently escaped from the pupa ; 5 «5, ^ c, ^ d, indi- 

 \dduals extracted from the pupae, for comparison 



9 



