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- 
eated. The relation of this to distribution will be noted subsequently. 
PLATY HELMINTHES. 
Trematoda-— 
Diplodiscus sp.* 
Young trematodes belonging to this genus were taken from the ali- 
mentary tract of the larvee of Rana catesbiana Shaw during Feb., °11. 
They were free in the intestine of the amphibian larve. 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 larvie 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 
molluse 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 28, 710. The only evidence that these 
are the developmental stages of Diplodiscus is that Diplodiscus is the only 
trematode known from this pond. 
TROCHELMINTHES. 
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, Anurea aculatca Ehrenberg; Hydatina senta 
Ehrenberg, and Monostyla lunaris 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. 
3Tdentified by Prof. H. B. Ward, 
