408 



ing. The amount of drying to which they had been subjected seems to be 

 near the limit for the species. They do not recover if completely desic- 

 cated. The relation of this to distribution will he noted subsequently. 



PLATYHELMINTHES. 



Trematoda — 

 Diplodiscus sp.^ 



Young trematodes belonging to this genus were taken from the ali- 

 mentary tract of the larvie of Rana cateshiana Shaw during Feb., '11. 



They were free in the intestine of the amphibian larvae. The contents 

 of the digestive tract of the worm seemed to be derived from the surround- 

 ing medium, i. e., the food material in the intestine of the "tadpole." Sex- 

 ually mature individuals were taken from larva^ of the same frog about 

 one month later (Mar. 20, '11). I have been unable thus far to determine 

 the invertebrate host of this trematode in this pond. The most numerous 

 mollusc is Luccinea retusa Lea. But many dissections have failed to reveal 

 trematode infection. 



The following intermediate stages taken with the plankton catches in 

 the open water have been noted. One cercaria on each of the following 

 dates: May 5, '09; Jan. 11, '10; Apr. 15, '10. 



A ciliated larva was taken May 2S, '10. The only evidence that these 

 are the developmental stages of Diplodiscus is that Diplodiscus is the only 

 trematode known from this pond. 



TEOCHELMINTHES. 



Ten rotifers were identified from the pond. Others were observed 

 occasionally but were not identified. Their rare occurrence, and the fact 

 that the methods used in the preservation of the material were not 

 especially adapted to rotifers, often rendered exact identification im- 

 possible. 



Of the ten rotifers, three, AnurcFa aculatea Ehrenberg; Hydatina senta 

 Ehrenberg. and Monostyla liinaris Ehrenberg, occurred in quantity in the 

 open water of the pond. The first was common in 1908, the other two in 

 1910. The other five were never common. 



^Identified by Prof. H. B. Ward, 



