471] LARVAL TREMATODES—CORT 25 



from Goniobasis virginica obtained near Princeton, New Jersey. In 1911 

 Cary sent me some of the material which he had used in the prepara- 

 tion of this paper, including specimens of Diplodiscus temporatus from 

 his experimental tadpoles. A study of this material and a careful anal- 

 ysis of Cary's account has convinced me that he has described in this 

 paper, two different species of larval trematodes neither of which 

 belong to Diplodiscus temporatus. 



The snails of the species Goniobasis virginica which he collected 

 from the Delaware and Raritan canal near Princeton in the fall of 1908, 

 contained rediae in which cercariae were developing, but those collected 

 from the same locality in the spring of the following year and those 

 from the Delaware river near Trenton, contained sporocysts in which 

 cercariae were developing. Cary assigns both these stages unhesitat- 

 ingly to the same species, for no other reason so far as can be judged 

 than that they were collected from the same species of snail from the 

 same general locality. That in the same species of trematode, cercariae 

 should be found developing from both sporocysts and rediae is without 

 parallel. Further in his own descriptions Cary shows that he is deal- 

 ing with two separate types of larvae. In connection with his account 

 of the development of the cercariae in the sporocysts, (p. 643), he 

 writes of the cercaria. 



"In the dorsal part of the sucker (oral sucker) there is developed 

 the dart (Stachel). This lies in a thin structureless sheath between 

 the muscle cells. It is shaped like a short arrow with a comparatively 

 broad head." 



Neither in the description nor in the figure (Cary, 1909, PL 30, 

 Fig. 6) of the cercaria which develops from a redia is a dart shown. 

 Further a comparison of the cercariae developing from rediae with the 

 others developing from sporocysts from the material which Cary sent 

 me, shows that they are entirely different in practically every character. 

 Figures 26 and 27 are drawings made to scale of these two types of 

 cercariae. According to Liihe's (1909) classification of the cercariae 

 these forms would fall into two entirely unrelated groups. The smaller 

 one with the boring spine which develops in the sporocysts (Fig. 26) 

 very evidently belongs in the Xiphidiocercariae (Liihe, 1909:189-200) 

 while the larger form agrees with the characteristics of the Gymno- 

 cephalous cercariae (Liihe, 1909:182-186). That two such diverse cer- 

 cariae should develop into the same adult is utterly impossible. Since 

 in his infection experiments Cary uses only the cercariae which develops 

 from rediae, he certainly can have no evidence that the cercariae 

 which develops from sporocysts and are entirely different from the 

 first type have any connection whatever with Diplodiscus temporatus. 



