No. 549] 



A CASE OF VOLYMOllPinsM 



543 



immediately examined not one differed outwardly from 

 the brightwelli type. But examination of the t tophi 

 yielded the astonishing result that in every instance they 

 bore a strong inner tooth in the exact position in which 

 this is found in A. amphora. 1 examined large numbers 

 of them and found that in all the features which I could 

 study with the facilities 1 had in the field, there was no 

 obvious variation whatever. It should be mentioned t hat 

 in outline these trophi presented the close approach to a 

 perfect oval which is characteristic of the bright irrlli 

 type. The strong inner tooth alone gave them decidedly 



This discovery is plainly again confusing, as to specific 

 distinctions between the types. Fortunately, however, 

 it serves at least to Hear up certain contradiction- in the 

 literature of the subject. Eousselet, in the article above 

 mentioned, dealt especially with this point. He figures 

 the jaws of A. brightwelli, to use his own expression, as 

 he has "invariably found them" — i. e., with an oval out- 

 line and without the inner teeth. He concludes that the 

 earlier writers on the genus— Dalrvmple, Brightwell, 

 Hudson— had certainly confused two different species of 

 Asplanchna, describing the trophi of A. amphora as be- 

 longing to A. brightwelli. 



My examination of the Sylvan Lake material shows 

 that no such error need be ascribed to them. A. bright 



myself have don^inmy own vicinity; while Brightwell 

 very probably found and described * the other, which I 

 have found so abundant in the South Dakota lake. 



The finding of A. brightwelli with two distinct types 

 of trophi may seem but a trivial matter, but taken in its 

 full connection it is not without interest. A. bright urlli 

 seems, in general, an all but constant species. Yet, judg- 

 ing by morphological test, it should be closelv related to 

 A. amphora, a species which experiment shows to be 

 phenomenally variable. 



