168 



THE AMERICAN NATURALIST 



[Vol. LI 



Spirogyra, Zygnemea, Mougeotia, etc., Desmids and Dia- 

 toms abundant. Water kept pure and cool by influx from 

 small rills or by seepage from adjacent stream. Tem- 

 perature of water, cir. 60° F. 

 Predominant forms : 



Chilodon cucullus, numerous Holostichia vernalis, numerous 



CMlomonas paramoecium, abundant Monas sp., abundant 



Coleps hirtus, numerous Pararrwecium lursaria, numerous 



Other forms present in less numbers (few or rare) : 



Arruieha proteus Euglena viridis 



Euglypha alveolata 



Euplotet 



Chlamydomonas sp. Loxophyllum sp. 



Colpoda cucullus Nostolenus orbiculari 



Cyphoderia ampulla Oxytrichia iifaria 



Ballasia frontinia Oxytrichia pellionella 



Difflugia acuminata Paramecium cav^atv 



Dileptus Tnonilatus Stylonychia pustulata 



Euglena deses Stylonychia putrina 



Dileptus gig as (Fig. 16) is surely the king of beasts 

 among the ciliate Protozoa. It is entirely carnivorous and 

 its appetite is apparently insatiable. The prey is stung 

 by the well developed trichocysts which Dileptus bears 

 upon its long ''neck" and if too large to be swept into the 

 buccal cavity by the cilia is forced in by the writhings of 

 the ''neck." The creature varies greatly in size, but is 

 normally about 450 microns in length. Individuals have 

 been reported measuring 800 microns ! 



Envieonmental Type No. V : Pools Choked with Alg^ ; 

 Water Warm 



Ditches and pools choked with heavy, luxuriant masses 

 of algae {Spirogyra, Ulothrix, Zygnemea, etc.) and ex- 

 posed to the sun during the entire length of the day. Cy- 

 clops, Canthrocamptus, Gammarus, Daphnia, Cypris, 

 Simocephalus, etc., abundant. In lesser numbers : aquatic 



