52 FEESH-WATEE EHIZOPODS OF NOETH AMEEICA. 



globules which appeared to be water- vacuoles. These larger Amcebse. gen- 

 erally contained a considerable quantity of food, mainly consisting of 

 diatoms of the kind which abundantly occurred in the water with the 

 animals. In several instances I observed individuals in the act of dis 

 clmrging dead shells of diatoms, as represented in the figure just indicated. 

 The expulsion occurred at the posterior end of the body; nothing escaped 

 except the remains of the food, and subsequently all trace of the tempo- 

 rary vent disappeared. 



None of these Amoebse exhibited anything like a posterior villous 

 process, though the end of the body appeared in some degree prehensile, 

 as several individuals were observed with adherent diatoms trailing after 

 them. 



Some water with growing Nitella gathered in the autumn was pre- 

 served during the winter In January, the surface of the sediment contained 

 multitudes of minute Amoebse, such as are represented in figs. 17-20, pi. 

 VIII. In their movements they exhibited considerable variety of form, but 

 were commonly more or less ovoid or clavate, and moved with the broader 

 extremity forward. They were composed of pale delicate endosarc, pre- 

 ceded by thick watch-crystal-like extensions of clear ectosarc. The endo- 

 sarc contained a round or oval nucleus, two or three contractile vesicles, 

 and a few scattered, darkly outlined granules, but no conspicuous food. 

 They ranged from 0.03 to 0.04 mm. in length. The posterior extremity 

 was prehensile, but exhibited no clear trace of a villous process. 



Some ditch-water, with ooze and portions of the root of the Arrow 

 Arum {Peltandra virginica), collected in autumn and examined the follow- 

 ing April, contained many small AmoebfB in association with large and 

 characteristic ones of Amoeba pro'.eus. The small Amoebse were habitually 

 ovate, more or less pyriform or clavate in shape, figs. 24-26, and ranged from 

 the ^th to the j^th of a millimetre in length. They moved actively onward 

 in a sort of rolling manner, with tlie broader extremity forward ; and the 

 posterior tapering end was devoid of any appearance of a villous process. 

 The endosarc contained many fine, irregular granules, which appeared to be 

 starch-particles ; and among them were others which appeared indistinctly 

 to be crystalline. A small nucleus and a contractile vesicle were constantly 

 present Among the little Amoebse a number were observed, apparentlj'^ of 

 the same kind, but containing a lai-ge spherical, granular nucleus, reaching 



