1 I I THE AMERICAN MONTHLY [Apiil 



lions a form — I'etaloiiKiiiMs iiit'^iil.-nis, oKserv <*(i li\ liim- 

 self, which althougli lieinu ■"' l»i' lar^ci- t li.-m this one, 

 hears a I'losc reseinhiaDcc, lie t'aih'd to ioc-.te the coii- 

 tractile vesicle and tlu^ nnch-ns and in conseiiuence h-aves 

 a doubt as to whethci- his i'eta lonionas irregularis is the 

 same as tiiis form. This iiifnsorian is dissimilar fi'om 

 any other of the species so far lecorded, in being devoiil 

 of a I'idge and of a farrow. When first observed, the 

 writer was inclined to plaee it among the genus Para 

 monas. hut on closer nxamiuat ion it was found 'o conform 

 in every detail of haliit with the geuus in which it is 

 placed. 



Family. — Paiamonadida'. S. K. 



Geuus. — Atractonema. Stien. 



Species. — Atractonema fusit'ormis (fig. 6). 

 iU)dy fusiform, cylindrical, more than twice as long as 

 wide : widest at the center and attenuate at lioth ex- 

 tremities; the anterior transversly truncate; posterior 

 obtusely {)ointed and at times produced in a nipple-like 

 process; pharynx distinct and extending baci<wards, 

 meeting tlie contractile vesicle, which is conspicuous and 

 centrally })laced : ilagellum more than one body length ; 

 nucleus round and medianly placed in postei-ior body 

 half; tMuloplasm hyaline and slightly granular; locomo- 

 tion slow and even. .^ize 1-I4(t0 imh. Habitat — rond 

 water with alga'. 



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

 that make this form different from Atractonema teivs. 

 Stien. 



Family. — Anisoncmida-. S. K. 



(lenus. — Diplomastix. S. K. 



Species. — Dijilomastix rostrum (fig. 7). 



Body elliptical, cylindrical and variable in size ; from 



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



truncate oldiqutdy to ventrum; this ti'uucation being 



slightly ct)ncave and pi'oducing the anterior into almost 



