No. 588] POPULATION OF " BLANKET-ALGJE " 757 



moving by jerks and sudden dartings hither and yon. 

 The minute form, Euplotes, has a peculiar method of loco- 

 motion that looks like walking along a filament, though it 

 is merely forward progress by means of cilia. 



The flagellates were represented by Euglena, Distigma 

 and Phacus, of which the first was fairly constant. Three 

 heliozoans, Actinosphcerkim,AcUnoplirys and Vampyrclla, 

 appeared infrequently. Hydra was found in one collec- 

 tion only, and no other coelenterates were seen. 



Various worms, mainly the microscopic nematodes as 

 well as unidentified planarians and turbellarians, also 

 three kinds of oligochsetes, namely Neds, Tubifex and 

 Chat og aster, were frequent but not regular inhabitants of 

 the alga-mass. 



The rotifers were regularly a part of the population, 

 furnishing species of eighteen genera. Determination of 

 genera was not undertaken until March The genus most 

 constantly in evidence was Diglena, especially in dirty 

 water, foraging industriously, nibbling and pulling at the 

 algae. A species of Metapidia with a broadly curved 

 lorica was seen several times. It clung by its toes to 

 debris, while the flow of water carried food-particles past 

 the rotating cilia into the mastax. Anurea, Salpina and 

 Synchceta were found exclusively in the pool nearest Cay- 

 uga Lake, pool A. Also in this pool, as well as elsewhere, 

 were found Polyarthra, Rotifer, Adineta, Diglena, Noth- 

 olca labis and a long-spined species of Rattulus. This 

 permanent pool and a similar pool (X 1 ) of the highland 

 were richest in rotifer life. Forms found in the latter 

 pool and not observed elsewhere, were Notommata and a 

 species of Stephanops with a fan-like anterior projection 

 of the lorica. Other genera identified were Brachionus, 

 Philodina, M ytillina., M astigocerca and Diaschiza. Chceto- 

 notus, a representative of the Gastrotricha, was seen a 

 few times. 



The Gastropoda, the only mollusk group represented, 

 did not furnish a constant element, since only eight collec- 

 tions contained any snails. Lymnea appeared once, 



