MORPHOLOGY AND BIOLOGY. 15 



high power be used in the examination, the endo- 

 plasm is observed to be composed of a delicate mesh- 

 work containing within it numerous granules which 

 vary in size in different species. These granules have 

 been termed " microsomes " by some authorities. As 

 a matter of fact they differ in nature, some being 

 due to undigested particles of food, some to chromidia, 

 some to waste materials, while others consist of mi- 

 nute crystals or oil droplets. According to Butschl the 

 entire cytoplasm of these organisms is composed of a 

 fluid substance contained within a meshwork com- 

 posed of another fluid of different composition. 



The endoplasm may be more or less refractive 

 and may contain, besides the nucleus, one or more 

 vacuoles ; threads, granules, and masses of chromatin 

 (chromidia) ; various crystals derived from the sur- 

 rounding media; bacteria of various kinds; and red 

 blood corpuscles in the case of the pathogenic amoebae 

 of man. 



The NUCLEUS varies in size, structure and shape 

 in different species of amoebae, and is of considerable 

 service in distinguishing between such species. A 

 visible nuclear membrane is observed surrounding the 

 nucleus in some species, while in others such a mem- 

 brane cannot be distinguished. In some species a 

 distinct karyosome can be seen, generally situated 

 near the centre of the nucleus, and this sometimes con- 



