82 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



less so than Amoeba verrucosa. When about to move, it commonly assumes an 

 oval and then an ovoid or a pyriform shape. It slowly glides with the thicker 

 end in advance, usually projecting from the front a conical eminence of 

 hyaline ectosarc. At the same time it quickly projects from one or both 

 sides of the head a long subulate pseudopod. Simultaneously, or more or 

 less successively, a variable number of similar pseudopods may be pro- 

 jected from other portions of the body. The pseudopods are more fre- 

 quently confined to the fore part of the body. There may be but one or 

 two, or they may be numerous and project everywhere except at the pos- 

 terior extremity. The latter is covered with papillae, differing from the 

 pseudopods in being short and blunt. See pi. VI. 



The pseudopods present considerable uniformity both in shape and 

 size. They are composed of the ectosarc alone, except that a few mole- 

 cules of the endosarc extend a little way within their base. They are elon- 

 gated conical, with an expanded base, slightly swollen near the middle, and 

 tapering to a sharp point. Occasionally one or two are forked. They make 

 their appearance from the ectosarc, suddenly, as short conical projections, 

 which run outwardly some distance with a blunt extremity, and then 

 rapidly extend in a tapering point, as exemplified in the group of pseudo- 

 pods to the right of the head in fig. 2, pi. VII. They are projected quickly 

 even to such a degree as to require special attention to see them produced, 

 and they are also as quickly retracted. 



The papillae of the back end of the body are variable in number and 

 appearance. Sometimes they are comparatively few; at others, numerous 

 and thickly crowded. Not unfrequently they are themselves papillose. 

 Their usual form is mammillary, often enlarged at the end, or they may be 

 conical and pointed. They are composed of the ectosarc, but commonly 

 receive more of the endosarc than the pseudopods. They appear to be 

 retractile, like the latter, and often diminish or increase ; often and quickly 

 change their aspect, and frequently disappear altogether. 



A remarkable feature of Dinamoeba (pi. VI) is seen in ever}' part of 

 the surface, including the pseudopods and posterior papillae, bristling with 

 exceedingly minute spicules, or rigid cils, which are directed perpendicularly 

 to the surface. Not unfrequently these minute cils are absent, figs. 2, 3, 

 5-9, pi. VII ; and in several instances in which they were abundantly 

 present, after some hours, on the same individuals, they had disappeared. 



