244 - College of Forestry 
ally the liver and the percentage of infestation ranged from 
1.50 to 18. 
In Europe several species of trematode worms find their 
intermediate host in mollusks, and the two species cited below 
are added to show that these worms are parasitic in several 
kinds of animals during their life history (Baker, 1911, b, 
p- 41, cited from Cooke, 1895, pp. 61, 62). Many of the 
American species probably have similar life histories. 
Distoma endolabrum Duj. Fluke. 
This worm first enters as host Lymnea stagnalis or 
Lymnea ovata; then Lymnea stagnalis or one of the fresh- 
water shrimps; and attains sexual maturity in the common 
frog. 
Distoma ascidia von Baer. Fluke. 
This worm passes first through Lymnea stagnalis or Plan- 
orbis corneus; secondly, through certain flies and gnats, or 
other insects (Chironomus, Perla, Ephemera); and finally 
matures in certain species of bats. 
10. Aue Living IN AND UPON THE SHELLS OF MOLLUSKS. 
The shells of mollusks are affected more or less seriously 
by boring plants (alge) which perforate the shell, destroy- 
ing the protective horny epidermis and permitting the car- 
bon dioxide in the water to dissolve the carbonate of lime of 
which the shell is composed. Several species of algee have 
been observed on and in the naiad shells of Connecticut. The 
same effects were observed in the Unto shells of Oneida Lake, 
and probably the same species of algze occur. Those described 
by Collins (1897, pp. 95-97) from Twin Lakes, Salisbury, 
Litchfield County, Connecticut, are as follows: 
Plectonema terebrans Born and Flah. 
““ Abundant all through the shells, and when the latter were 
decalcified, formed a dense mat, which made it rather difficult 
to distinguish the other algz, that grew in company with it” 
(p. 95). Also common in marine shells on the shores of Long 
Island. 
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