CHAPTER IV 



FIBRILLAR SYSTEMS IN CILIATES 

 C. V. Taylor 



Introduction 



The essential nature of Leeuwenhoek's "little animals" remained 

 obscure for more than 150 years, evidently because the methods of ob- 

 servation which characterized that ingenious microscopist of Delft were 

 replaced largely by fruitless speculation. Otherwise, man's epochal dis- 

 covery of the cellular nature of living things might have been realized 

 sooner. 



Meantime, it is true, a prodigious diversity of macroscopic forms had 

 been examined and classified. But the disclosure of cellularity, which 

 eventually unified all of this diversity in organic form, had to depend 

 upon the detailed analysis of organic structure. 



During the hundred years that have now intervened, that common 

 denominator of organic form and function has come to be regarded, for 

 multicellular plants and animals, as a sort of master key to the solution 

 of their fundamental problems. And for the major advances in biology 

 during that memorable century, we are surely indebted primarily to this 

 cellular concept of the organization of living things. 



For the microorganisms, however, the concept of cellularity, although 

 generally conceded, has encountered not infrequently some confusing 

 difficulties. With von Siebold's pronouncement in 1845 of the unicellu- 

 larity of the Protozoa, the way at first seemed clear toward simplifying 

 and unifying all forms of life, in terms of the cell as the universal 

 unit. Eventually, however, it was evident that, for the Protozoa, this 

 concept did not simplify matters so satisfactorily. The chief difficulty 

 here arose in trying to equate the protozoon cell with a tissue cell of 

 the Metazoa. And even in recent times this comparison has again been 

 challenged by Dobell (1911) and others, who would maintain that 

 Protozoa are not cells at all and so should be regarded as non-celluar 

 organisms. 



