Fig. 42. Invertebrate animals from 100 square feet on a log covered with fila- 

 mentous algae (Cladophora fracta, CEdogonmm species), Habitat No. iv, Field 

 No. 708, water 5 feet deep. The principal species are Bythinia tcntacuJata, 

 Amnicola bakerimia niniia and Hyalella knickerbockeri. 



