CHARACTERS OF AMCEBA 27 



are fairly common, and as many as four may be 

 present. 



Characters of the Amoeba. The average diameter 

 of the body of the organism is about 20 p. It 

 consists of a finely granular endoplasm surrounded 

 by a very narrow layer of clear ectoplasm which is 

 increased in amount in one direction, presenting 

 an appearance of the granular portion having 

 shrunk away from one side. The endoplasm 

 contains the usual contractile vacuole, food 

 vacuoles, ingested bacteria, moulds, and debris of 

 all kinds, and a vesicular nucleus showing a dis- 

 tinct karyosome. The movements are fairly 

 active, the pseudopodia being lobose in type, and 

 progression is by crawling. In comparison with 

 Amoeba proteus it is less active, much smaller, 

 and imports its food rather than seizes it. It has 

 not, however, the rolling motion of A. verrucosa 

 nor the slug-like crawl of a typical limax amoeba 

 (PL VII.). The nucleus is usually single, some- 

 times double, and occasionally multiple, the 

 greatest number yet seen in a single cell being 

 six. The size of the amceba is no indication of 

 the number of nuclei, one of the largest observed 

 being mononuclear, and some quite small ones 

 having been seen containing as many as four 

 nuclei. The nucleus occupies a changeable position 

 in the endoplasm, and is subject to considerable 

 alterations in shape owing to the movements in 

 the surrounding protoplasm. A centriole, possibly 

 a centrosome or nucleolus, may often be seen 

 either in the unstained condition or when stained 

 by the jelly method (PI. V.). In large nuclei small 

 circular spots can be observed alternately light 



