58 FRESH- WATER RHIZOPODS OF NORTH AMERICA. 



blance to Amoeba verrucosa ; but others, in their larger size, ranging from 

 0.35 to 0.4 mm., and in the possession of a terminal villous process, remind 

 one more of Amoeba villosa. With the exception of the latter forms, A. 

 terricola and A. verrucosa agree closely in characters: the exceedingly- 

 sluggish habit, the indisposition to move, the great porportionate extent 

 and membrane-like appearance of the ectosarc, the wrinkled condition of 

 the surface, and the short pseudopodal extensions, are the same in both. 



The Protamoeba simplex of Prof. Haeckel* likewise bears a close resem- 

 blance to Amoeba verrucosa ; but, according to the character assigned to the 

 former, a contractile vesicle and nucleus are absent, while they are present 

 and more or less conspicuous in the latter. 



AMCEBA RADIOSA. 



Plate IV, 'figs. 1-18. 



Amoeba radiosa. Ehrenberg : Abh. Ak. Wis. Berlin, 1830, 39 ; 1831, 80 ; Infusionsthierchen, 1838, 128, Taf. 

 viii,Fig.xiii.— Dujardin: Infusoires, 1841, 23G, pi. iv, figs. 2, 3.— Perty: Kennt. kleinst. Le- 

 bensformen, 1852, 188.— Carter : An. Mag. Nat. Hist. 1850, 243, pi. v, figs. 10-18. 



Amoeba brachiata. Dujardin : Infusoires, 1841, 238, pi. iv, fig. 4.— Fromentel : Etudes Microzoaires, 347, 

 pi. xxix, fig. 4. 



Amoeba ramosa. Dujardin: Infusoires, 1841,239, pi. iv, fig. 5. 



Comparatively small, colorless, transparent, inactive. As usually ob- 

 served floating, habitually stellate, with a spheroidal or oval central mass 

 or body, and from two or three to a dozen or more pseudopods of variable 

 length and form, mostly conical and acute or attenuated and thread-like, 

 commonly simple, straight, curved or flexuose, rarely furcate. In creep- 

 ing, of a less radiate character, but with the pseudopods mainly divergent 

 from one extremity, and that in the direction of motion of the animal. 

 Usually one conspicuous contractile vesicle or several smaller ones. Nu- 

 cleus usually distinct. Endosarc with a few oil-like molecules, sometimes 

 more or less replete with water-vacuoles. Food commonly scanty. 



Size.— Body 0.012 mm. to 0.045 mm. diameter or rarely to 0.06 mm.; 

 pseudopods to 0.08 mm. long. 



Locality. — In the ooze and among aquatic plants of most ponds, ditches, 

 and springs. Pennsylvania, New Jersey, Rhode Island, Connecticut, 

 Maine, Nova Scotia, and Fort Bridger and Uinta Mountains, Wyoming. 



Ehrenbenr described a small form of Amoeba under the above name, 



' S udien ueber Moneren u. a. Protisten, 1870, 172, Taf. vi, Fig. 12. 



