114 THE AMERICAN BIONTHLY [April 



tioiis a forjn — Petaloinonas irregiilari.s, observed by him- 

 self, wliich although being a bit larger than this one, 

 bears a close resemblance. lie failed to locate the con- 

 tractile vesicle and the nnclcns and in consequence b-aves 

 a doubt as to whether his I'etalomonas irregularis is the 

 same as this form. This infusorian is dissimilar t'roui 

 any other of the species so far recorded, in being devoid 

 of a ridge and of a furrow. When first observed, the 

 writer was inclined to place it among the genus Paia 

 raouas, but on closer examination it was found to conform 

 in every detail of habit with the genus in which it is 

 |.)laced. 



Family. — Paramonadid?e. S. K. 



Genus. — Atractonema. Stien. 



Species. — Atractonema fusiformis (fig. 6). 

 Body fusiform, cylindrical, more than twice as long as 

 wide ; widest at the center and attenuate at both ex- 

 tremities; the anterior transversly truncate; posterior 

 obtusely pointed and at times produced in a nipple-like 

 process ; pharynx distinct and extending backwards, 

 meeting the contractile vesicle, which is conspicuous and 

 centrally placed; Hagellum more than one body length ; 

 nucleus round and medianly placed in posterior body 

 half; endoplasm hyaline and slightly granular; locomo- 

 tion slow and even. Size 1-1400 inch. Habitat — Pond 

 water with algse. 



The small size and the ratio of width to length are all 

 that make this form different from Atractonema teres. 

 Stien. 



Family. — Anisonemida?. S. K. 



Grenus, — Diplomastix. S. K. 



Species. — -Diplomastix rostrum (fig. 7). 



Body elliptical, cylindrical and variable in size ; from 



one and a half to three times as long as wide ; anterior 



truncate obliquely to ventrum ; this truncation being 



slightly concave and producing the anterior into almost 



