60 DEVELOPMENT OF 



the same time, I observed very clearly that the surface of 

 the abdomen was hoUowed out in a broad hne, extending 

 from the coUar to the discoid acetabulum, between which 

 and the posterior end of the body I noticed in several 

 individuals a spot composed of transparent globules or 

 cells, within which again were two contiguous clear 

 specks, the whole of which I could only look upon as the 

 transparent ends of the forked intestine, surrounded by 

 the hepatic substance. The animals represented by 

 fig. 8 c, % d, are more advanced. In fig. 8 c, the spines 

 had recently fallen off, leaving evident traces of their at- 

 tachments on the upper surface of the collar ; fig. 8 d, on 

 the contrary, had lost all trace of the spines, and its collar 

 was much smaller. The abdominal acetabulum was also 

 smaller, and had lost its cup-like form. The liver-like 

 organ, and the caecal prolongations of the digestive cavity 

 surrounded by it, were in all these individuals of unusual 

 width. 



Finally, figs. 8 e, and 8 /, represent this fluke as I 

 met with it, to the number of 10 — 12 individuals in the 

 liver of some snails {Limntsus stagnalis^ on the 6th of 

 August, 1841. These snails had been taken in a place 

 much exposed to the sun, at a sea sluice near Grase. 



The Distomata difiered from those described above, 

 which I afterwards found beneath the skin of the snails, 

 especially in their greater sluggishness of motion and the 

 more homogeneous, parenchymatous consistence of the 

 substance composing the body. No external trace of 

 longitudinal or transverse muscular fibres was visible, 

 although the individuals figured in 8 c and 8 d, pre- 

 sented distinct and regular transverse riig^B, and performed 

 very lively movements during their contractions. 



Thus, the deeper these creatures had penetrated into 

 the body of the snail, and into the substance of the indi- 

 vidual organs, the more of their own organization did they 

 appear to lose. Both the oral and abdominal acetabula 

 became proportionably smaller, although from the situa- 

 tion of the animal it was not possible that their size should 



