58 OSBORN. [Vol. II. 



was in this organ that the great mass of Aspidogasters was 

 obtained ; and, generally, they were found closely packed into 

 the anterior corners, at the entrance into the kidney and peri- 

 cardial gland. In these latter organs I have found a good num- 

 ber, too, but in no other organ have I succeeded in finding any, 

 although I have taken considerable trouble to find evidence of 

 the migration of the young animals." And a similar impres- 

 sion is given by Huxley ('72), Hoyle, Encyclopaedia Britannica, 

 XXIII, p. 540, and Monticelli ('92), as well as in most of the 

 current text-books, etc. 



Its situation is also quite unlike that attributed by Poirier to 

 Platyaspis lenoiri, which is an internal parasite of the turtle. 

 We do not know that Platyaspis does not have two hosts, but 

 the supposition is unlikely in view of the habits of the family 

 Aspidobothridae, and if it should prove to be the fact that it 

 has only one, then these two Platyaspid forms are very differ- 

 ent indeed in their host relations. 



I am not prepared at present to say much about the host dis- 

 tribution of the parasite, but I can say that in Lake Chautau- 

 qua it is chiefly but not absolutely confined to Anodonta. 

 The following Unionidae have been recognized growing in 

 close proximity : Anodonta plana Lea, Unio hiteolns Lam, 

 U. edentnla, U. pJiaseolns Hid., U. gibbosiis Brns. ; and while 

 Anodonta seems to be the most usual host, the parasite has 

 been noticed rarely in U. luteohis. I have not met with 

 Aspidogaster at Lake Chautauqua, but as it is an endoparasite 

 it may easily be present there and have escaped my notice, 

 since I have not made a point of searching carefully through 

 the pericardium and other organs in which it is reported as 

 likely to occur. I do not, however, imagine that it is very 

 common, for, in case it were, it would surely have attracted 

 attention during the many dissections that have been made by 

 the students. 



I have not as yet made a strict study of the habits of the 

 parasite. On opening the mantle cavity of the host in air, one 

 of course subjects the parasite to very unnatural conditions; at 

 such time it adheres to the surface of the host by means of its 

 enormous and highly complex ventral sucker, and its anterior 



