260 CILIATE FIBRILLAR SYSTEMS 



functions to the exclusion of another possible function or functions, then 

 surely that investigator thereby adopts a point of view which is incon- 

 sistent and indefensible as well. 



In such instances we begin to sense a recrudescence of the opposing 

 claims advanced in the Ehrenberg-Dujardin controversy and of the non- 

 cellular theory of protistan organization proposed by Dobell and others. 

 Once having denied the validity of Ehrenberg's extreme contention that 

 the organs of the Infusoria are essentially miniature counterparts of 

 those of macroscopic organisms, a comparably extreme viewpoint is sub- 

 stituted, which would maintain that the Protista represent a complete de- 

 parture in the organization of living things and so belong in the wholly 

 exclusive category of non-cellular organisms. Thus the claims of these 

 counter extremists would have us search for identities in organization, on 

 the one hand, or only for differences in protistan and multicellular or- 

 ganization on the other hand. 



In Ehrenberg's day similar extreme points of view were quite irrec- 

 oncilable, but in our day they can scarcely represent anything less than 

 rash inconsistencies. Obviously the thesis of non-cellular organization 

 tends to place exclusive emphasis on differences between protozoan and 

 metazoan organization and, if one is still inclined to accept that thesis, 

 one might well refer to Belaf's (1926) excellent monograph on the 

 protistan nucleus. Variable as are the nuclei, in form and behavior, of 

 the many kinds there described and illustrated — where they appear to 

 diifer from one another more than some differ from metazoan nuclei — 

 surely one cannot fail to recognize that their numerous modifications do 

 not represent discrete differences, but clearly betray the indelible marks 

 of a common origin. They are like the musical variations of some great 

 motif. They demonstrate irrefutably that living nature has been both 

 labile and stable in its evolutionary history, so that we are amply justified 

 in searching out and emphasizing not merely differences but also, and 

 more fundamentally, similarities, in both the structural and functional 

 processes of protoplasmic differentiation. 



And since all cellular differentiation is referable in its last analysis to 

 protoplasmic differentiation, then certainly the fibrils and fibrillar sys- 

 tems of multicellular tissues, such as those described by Grave and 

 Schmitt (1925), may belong in the same category, both structurally and 

 functionally, as some fibrillar differentiations that have been described 

 and some that we may afford further to search for, in unicellular organ- 



