32 ENTOZOA. 



" {}i,) — The yelk molecules surrounding the germinal vesicle 

 are not directly transformed into an embryo. On the contrary, 

 they only appear to part with a portion of their constituent 

 elements, which portion, in combination with the germ vesicle, and 

 by means of the latter, is employed in forming the embryonic cells, 

 whilst the other portion remains superfluous. Again, in regard to 

 the vascular system of trematoda, it is partly ciliated and partly 

 non-ciliated ; but, at all events, we find that the vessels have a 

 wall fiirnished with a lining of epithelium. There is little doubt 

 that the circulating fluid enters from without ; however, its 

 principal function is excretory. In some species, or in some 

 parts of the system, the excretory matters do not render the 

 circulating fluid turbid ; at other times it appears that they are 

 mixed with much solid matter which becomes excreted through 

 the caudal opening." 



Genera. — Fasciola, Linneus ; Gampula, Oobbold ; Distoma, 

 Zeder ; Dicrocoelimn, Dujardin, Weinland ; Bilharzia, Oobbold ; 

 = Gynoeco])'horus, Diesing; = Thecosoma, Moquin-Tandon ; = 8c]iis- 

 tosoma, Weinland ; Kolliheria, Oobbold ; Grossodera, Dujardin ; 

 Echinostoma, Dujardin ; Gasterostoma, Yon Siebold ; Wedlia, 

 Oobbold ; Godonocephalus, Diesing ; Eustemma^ Diesing ; Eolos- 

 toma, Nitzsch ; Remistoma, Diesing ; Di]}lostoma, I^ordmann ; 

 Bhopalophorus, Diesing ; Amjphistoma, Zeder ; AmpMptyches, 

 Grube and Wagoner ; Tylodelphys, Diesing. 



