44 THE PROTOZOA 



opaque, less refringent and coarsely granular ; the seat of trophic 

 and reproductive functions. 



These two zones of the protoplasmic body are, in the more primi- 

 tive forms, differentiations of the protoplasm more or less tem- 

 porary and transient in nature. For instance, in an amoeba which 

 is in active movement, fluid endoplasm is constantly flowing along 

 the axes of the pseudopodia towards their tips, where it comes into 

 contact with the surrounding medium, the water or other fluid in 

 which the amoeba lives. Under the influence of the medium the 

 endoplasm is converted into ectoplasm, becomes of stiffer, less fluid 

 consistence, and loses its coarse granulations. At the same time, 

 at the hinder end of the amoeba, ectoplasm is continually passing 

 into the interior of the body, where it becomes liquefied and granular 

 in structure, and is converted into endoplasm (Rhumbler, 34). 



In Protozoa, however, which do not exhibit amoeboid movement, 

 the ectoplasm and endoplasm may be two independent layers, well 

 defined and perfectly separate the one from the other. The ecto- 

 plasm is the seat of those functions which are connected with the 

 relation of the organism to the outer world, to the environment 

 in which it lives ; the endoplasm, on the other hand, is concerned 

 specially with the internal affairs, so to speak, of the protoplasmic 

 body. In the following two chapters the various organs of the 

 Protozoa will be considered under the headings of the layer from 

 which they are formed, and according to the functions they perform. 



Bibliography. For references, see p. 477. 



