70 FRESH-WATER EHIZOPODS OF NORTH AMERICA. 



According to Mr. Archer, Ourarnceba, with its appendages, which he 

 aptty likens to "a bundle of dipt-candles," may be only a varietal form of 

 what I have considered to be Amoeba proteus, but the solution of the ques- 

 tion remains for future investigation. 



One of the specimens of Ouramaiba vorax which earliest attracted my 

 attention did so on account of the unusual quantity and variety of diatoms 

 and other algae which it contained, rather than on account of its linear 

 caudal appendages. It was indeed this specimen, fairly represented in fig. 

 1 , that led me to adopt the specific name of the animal. The individual 

 was nearly a third of a millimetre in length, with the caudal appendages 

 one-sixth of a millimetre longer. It moved along in a flowing manner, 

 tongue-like in outline, with the narrower end forward, and without project- 

 ing any digit-like pseudopods. The caudal filaments at times trailed 

 behind ; at others, more or less diverged to the right and left. There were 

 six tufts, which would become distinctly separated, then would collect into 

 two bundles, and again would combine into a single one. Among the food 

 contents of the endosarc there were four large specimens of Navicula major, 

 besides several of Gomphonema, Stauroneis, and other diatoms, a Cosma- 

 rium, fragments of a bluish green Oscillaria, etc. 



Another individual of Ourarnceba, when first seen, formed a mulberry- 

 like mass, as represented in fig. 3. It measured about 0.14 mm. in diameter, 

 and presented five tufts of filamentous appendages projecting from one half 

 the mass. After a little while it elongated, lost its mulberry-like appear- 

 ance, and projected from the sides long digitiform pseudopods, as seen in 

 fig. 2. The animal in this condition measured about 3 mm. long, and the 

 five tufts of caudal filaments were widely separated and divergent poste- 

 riorly. The discoid nucleus and contractile vesicle were distinctly visible, 

 and agreed closely in appearance and habitual relative position with those 

 of Amaiba proteus. Food-balls and water-vacuoles were few. 



Another specimen, represented in fig. 4, had a branched appearance, 

 and afterward assumed a stellate form extending over a space of about 

 0.25 mm. It possessed but two tufts of short caudal filaments. 



A specimen from a collection of the following season, represented in 

 fig. 5, had a palmate appearance, which, as usual with the animal, changed at 

 eveiy movement. It measured 0.3 mm. in length, and had a large bundle of 

 filaments trailing behind, which measured up to 2 mm. in length. A lai'ge 



