60 FRESHWATER RHIZOPODS OF NORTH AMERICA. 



I have observed them in the proper material, collected from pools, ponds, 

 ditches, springs, bogs, and other situations in all seasons of the year, 

 excepting when that material has been exposed to the cold of winter ; and 

 I have found them from the head of the Bay of Fundy to Florida, and from 

 near the ocean level at Cape May, N. J., to an elevation of 10,000 feet in 

 the Uinta Mountains of Wj^oming Territory. 



Amceba radiosa, figs. 1-18, pi. IV, as commonly observed floating or 

 swimming, has more or less of a stellate form, with pointed conical rays 

 emanating from a common centre, or it appears as a spheroidal body with 

 a variable number of more or less tapering pseudopods. The central sar- 

 code mass or body ranges from 0.018 mm. to 0.06 mm. in diameter. The 

 pseudopods vary in number from one or two to a dozen or more, and consist 

 of extensions mainly of clear ectosarc. They vary greatly in length, — less 

 than the body to three or four times its diameter. Sometimes they extend 

 in long filaments, so as to assume almost the appearance of the rays of the 

 common Sun-animalcule. Usually they are moderately long, tapering, 

 conical, shai-p-pointed, straight, bent, or somewhat tortuous. Less fre- 

 quently they are more cylindroid, blunt, or pointed, mostly simple, and 

 rarely furcate. 



The endosarc of the body consists of a fine pale granular protoplasm, 

 with variable proportions, though in comparatively small quantity, of darker 

 molecules. It usually contains one or more food-balls enclosed in water- 

 drops, colored or colorless, and conspicuous for their size. These may be 

 altogether absent, or may be replaced by simple drops of water or other 

 liquid, the result of digestion of food. Sometimes many water-drops or 

 water- vacuoles, are present, as seen in fig. 13, pi. IV, and these at times 

 appear to multiply or decrease, while the animal is under observation. 



Among the constituents of the endosarc, a round nucleus is usually to 

 be detected, though sometimes it is much obscured by surrounding mate- 

 rials, and occasionally cannot be distinguished without the action of 

 reagents upon the animal. 



The contractile vesicle is constantly to be observed exhibiting all the 

 phenomena noticed in it in most Fresh-water Rhizopods ; but frequently, 

 in accordance with the genei'al sluggish nature of this formpf Amoeba, its 

 movements are exceedingly slow. 



Occasionally a diatom or other alga may be observed among the con- 



