44 FRESH- WATER RHIZOPODS OF NORTH AMERICA. 



bibed from the vacuoles into the contiguous enclosarc, the vesicles of ecto- 

 sarc which contained the food and water undergo resolution into endosarc. 



As the soft structure of Amoeba proteus is totally unprotected, even by 

 the thinnest membrane, one would expect to find the animal exceedingly 

 irritable, though such appears not to be the case in a marked degree. In 

 its wanderings it frequently comes into contact with more actively moving 

 Infusorians and mailed Rotifers without in the least being affected by their 

 rude shocks. On one occasion I happened to have beneath the micro- 

 scope a large individual of Amoeba proteus, together with a multitude of 

 the active ciliated Infusorian, the Coleps hirtus. The Amoeba moved about, 

 entirely indifferent to the frequent buffets of the Coleps. In attempting 

 to readjust the cover of the object-glass, a portion of the Amoeba was 

 crushed off; but notwithstanding the accident, the larger portion of the 

 creature, still retaining its nucleus and contractile vesicle, moved away, 

 apparently unmindful of its injury. The smaller portion of the Amoeba 

 was attacked by half a dozen Coleps, and the escaping granules of the 

 endosarc, exhibiting lively molecular movement, were greedily swallowed 

 by the Infusorian. One would further suppose from the structure and 

 semi-fluid character of the Amoeba that it must be sticky and that materials 

 would adhere as they came into contact with it. This is, however, so far 

 from being the case, that Amoeba proteus is frequently observed traversing 

 mud with algae and other materials, without anything adhering to its 

 surface even for a moment. Not unfrequently, however, various matters 

 are observed attached to the posterior extremity of the body, and dragged 

 after the animal in its movements. 



Amoeba proteus, like most others of the genus and its allies, is essentially 

 herbivorous, though its choice of vegetal food is perhaps largely due to 

 the fact that it is more readily attainable than animal food. Judging from 

 the materials usually observed among the constituents of the endosarc, the 

 favorite food consists chiefly of the one-celled alga;, diatoms, desmids, 

 zoospores, and portions of filamentous algae, besides fragments of the 

 tissues of higher plants. The Amoeba evidently possesses a power of 

 discrimination and selection in its food, for although it appropriates with 

 the latter many particles of dead vegetal tissues, and even abundance of 

 sand-grains, it commonly rejects dead diatom shells and the empty cells of 

 other algae. 



