MICHIGAN ACADEMY OF SCIENCE. 81 



THE PORIFERA, OLIGIOCHAETA, AND CERTAIN OTHER 



GROUPS OF INVERTEBRATES IN THE VICINITY 



OF DOUGLAS LAKE, MICHIGAN.* 



BY FRANK SMITH AND BESSIE R. GREEN. 



Little has been published concerning- the Michigan representa- 

 tives of certain groups of aquatic invertebrates. It therefore seems 

 advisable to make known the results of our observations on some of 

 these groups as represented in the vicinity of Douglas Lake in 

 Cheboygan County of that state. The observations were made by 

 the senior author during the four summers of 1911-1914 while on 

 the staff of the University of Michigan Summer Session at the Bio- 

 logical Station and by the junior author during the summers of 

 1911 and 1913, during the latter of which' she held a research 

 fellowship. 



The groups chieflj^ studied were the earthworms and the fresh 

 water-sponges, but a few additions were made to the lists of forms 

 known in the vicinit}-, in certain other groups. 



FRESH-WATER SPONGES. 



Nine species of sponges were found in the Douglas Lake vicinity 

 although none were collected in the lake itself. The wave action 

 is too violent in the shallower parts of the lake to permit such 

 development and we made but little search for sponges in the 

 deeper parts. Seven species were found in the streams connected 

 with the lake and in the beach pools along its shores. Along with 

 three of these species, two additional ones were found in a small 

 pond in what is known at the Station as Smith's Bog, about two 

 miles to the southeast. The list of species and localities follows. 



SpongUla fragilis Leidy. Abundant in Bessey Creek, beach pools, 

 and Smith's Bog. Also collected in Burt Lake and Indian River. 



Spongilla lacustris (L.). Common in Maple River. 



Ephydatia miilleri (Lieberkiihn). Common in Maple River. . Also 

 collected in Burt Lake, Crooked River, and Indian River. 



f Ephydatia fluviatilis (L.). Bessey Creek. We have tentatively 

 referred to this species a number of specimens which differ some- 

 what from the typical form but about whose exact status there is 



♦Contribution from the University of Michigan Biological Station No. 32. 

 II 



