GENUS AMCEBA— AMCEBA PEOTEUS. . 39 



Not unfi-equently during the extension of one oi* more pseudopods 

 in advance, another may originate, and extend in a widely divergent or 

 even opposite directioTi from the former. In such instances, after a Uttle 

 while, the previously advancing pseudopods become retarded in their course, 

 then recede, and go to contribute to supply the new pseudopod moving in 

 another direction. 



Occasionally clearer and wider expansions than usual of the ectosarc 

 appear at the root of a pseudopod, or like a web in the crotch of a pair of 

 pseudopods, as seen in figs. 3, 5, 7, pi. I. Similar expansions at times 

 extend as longitudinal folds along the body and principal pseudopods, as 

 represented in fig. 7. 



Sometimes a pair of pseudopods start together from near the same 

 point, extend side by side, and, as they advance, become confluent from 

 their root onward. Very rarely do contiguous pseudopods, approaching 

 one another and coming into contact at- the ends, become connate, or 

 fused together, though I have observed this to occur in the capture of an 

 animalcule, as represented in fig. 5 c, pi. I. 



The fundamental structure of Amoeba proteus consists of a thin, color- 

 less, jelly-like, pale, and finely granular protoplasm, or sarcode, endowed 

 with extensile, contractile, and other less well defined attributes, in which, 

 however, a chentiical or digestive power may be included. The exterior 

 clearer portion of the protoplasmic mass constitutes the ectosarc, while the 

 interior portion, mingled with various elements, intrinsic and extrinsic, con- 

 stitutes the endosarc. 



The clear ectosarc, examined by the higher powers of the microscope 

 under favorable conditions of light, appears never to be perfectly structure- 

 less, but exhibits an infinitely fine granular constitution. 



The endosarc, with its mingled coarser elements in its relationship with 

 the ectosarc, may be compared with the circulating blood in the capillaries 

 of the higher animals. The endosarc is comparable to the rapidly flowing 

 current of blood, mingled with its corpuscles, in the axes of the vessels, 

 while the ectosarc is comparable to the slower moving blood-liquor next 

 the walls of the vessels. 



The ordinarily distinguishable elements of the endosarc of Amoeba 

 proteus have appeared to me to be as follows : 



1 . Granules, from those of the finest, most diff'use, and scarcely per- 



