GASTEEO STOMA AMPHISTOMA. 37 



only a sliort stomaclial cavity, wliich. reminds one of the same 

 viscus in tlie imperfectly organized sporocysts or redige. The 

 yelk-forming glands exhibit conspicuous, round, secreting cells, 

 the testes being also largely developed. I have also noticed 

 two other small bodies, one of which probably represents the 

 ovary or germ stock, whilst the other may be referred to the recep- 

 taculum seminis, or posterior seminal vesicle of Yon Siebold. The 

 connection between these several organs is not seen in this 

 specimen, but their relative position is well shown. When the 

 species first came under my observation, I naturally followed 

 Rudolphi, who described this trematode as a distome {D. graci- 

 lescens, Eudolphi). I remember seeking most diligently for the 

 digestive tubes, being greatly puzzled, not merely by their absence, 

 but also by the character and position of an organ which we 

 now well know to be the sheath of the intromittent appendage. The 

 uterus also terminates in its immediate vicinity, opening externally 

 by a common outlet. The anatomy of this genus has been pretty 

 fully illustrated by Yon Siebold. According to Molin, the excretory, 

 water-vascular organ (or respiratory apparatus, as he interrogatively 

 puts it) consists (in Gasterostoma fimhriatum) of a broad central 

 tube occupying the entire length of the body. In connection with 

 this tube, he did not discover any branches, but he represents it 

 as a simple sac opening externally at the caudal extremity. 



Amphistoma. — The most marked character in this genus has refer- 

 ence to what may be styled the caudal position of the acetabulum, 

 which is also very largely developed, being two or three times 

 gi-eater than the oral sucker. This feature is admirably shown in 

 the copy here given of Blanchard's enlarged figure of Amphis- 

 toma conicum (Plate III. Fig. 1), the same species being also 

 represented by two other views where it is drawn twice the 

 natural size (Figs. 2 and 3). The digestive system conforms 

 closely to the true distome type, as do also the reproductive organs, 

 both of the male (Fig. 5) and female (Fig. 4). The ova in this 

 species are about l-150th of an inch long, and l-250th of an inch 



