40 AMEBOID MOVEMENT 



It is to be noted however that the more intimate structure of 

 streaming protoplasm cannot always express itself externally as 

 it can in ameba. As was suggested in the introduction, there is 

 no good reason for supposing that the causes of streaming in 

 the various organisms in which it is observed are fundamentally 

 different. The problem of ameboid movement cannot be consid- 

 ered apart from the streaming of protoplasm in foraminifera, 

 myxomycetes, plant cells, lymphocytes, desmids, diatoms and 

 ciliates. The streaming of endoplasm in some cells, such as in 

 ciliates and plant cells, does not give rise to change of shape of 

 the cell as it does in ameba. In these cases the character of 

 streaming is highly restricted; the unyielding ectoplasm or cell 

 wall as the case may be, prevents any but the most essential 

 features of streaming from occurring. Recalling the analogy of 

 crystallization, streaming in a plant cell or in a ciliate is analogous 

 to crystallization occurring in a tube or vessel too small for the 

 crystals to form properly. 



This discussion anent the fundamental chemical uniqueness of 

 each species of ameba is of course not complete without an exam- 

 ination of the views expressed to the contrary. And it is to this 

 side of the discussion that we may now briefly direct our atten- 

 tion. 



