40 



BIOLOGY OF THE PROTOZOA 



organizations and interactions of different protoplasmic substances 

 and which form the physical basis of inheritance. A minute frag- 

 ment of Uroleptus mobilis is difficult to distinguish from a similar 

 fragment of Dileptus gigas, yet the former develops into a perfect 

 Uroleptus, the latter into Dileptus. The encysted forms of many 

 types are impossible to identify until the cysts are opened and vital 

 processes begin again. These facts indicate that the finer or ulti- 

 mate composition of protoplasm is different in different forms and 



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c 





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Fig. 21. — Anthophysa vegetans. Colony of flagellates with iron encrusted gelatin- 

 ous stalks. X 1000. (After Doflein, Lehrbuch der Protozoenkunde, 1927, courtesy 

 of G. Fischer.) 



specific for each species, and justify the view that there are as many 

 kinds of protoplasm as there are species of Protozoa, Metazoa or 

 living things generally. Considerations of this nature inevitably 

 lead us into the lines of thought followed by Whitman, Gurwitsch, 

 Dobell and many others and to question again the adequacy of the 

 cell theory in its application to Protozoa. 



The specificity of protoplasm is not at all indicated by its appear- 

 ance, although obvious differences in many cases may be seen even 



