CHAPTER XX 



EXTENSIONS 



Having in hand the already considerable knowledge about Stentor, 

 we want to inquire into the relevance of these findings for general 

 problems of the organism. At present we cannot expect that these 

 bearings will be more than suggestive. For sound construction we 

 need to proceed step by step as far as we now can go. Since 

 physiological and biochemical studies of Stentor have only begun, 

 the discussion will necessarily be slanted in the direction of 

 epigenetics, or morphogenesis in the widest sense. 



I. Stentor and other ciliates 



That the performance of Stentor as revealed by experimentation 

 is not unique may be shown by comparing its behavior with that 

 of Blepharisma, the only other ciliate on which extensive studies 

 in experimental morphology are available. Since my investigations 

 and the remarkable studies of Suzuki (1957) were pursued indepen- 

 dently, paralleling of results on many points is the more striking. 

 Suzuki reported within a single publication which deserves to 

 become a classic a series of experiments encompassing what would 

 seem to be nearly the whole range of possibilities in Blepharisma. 

 Although these animals were not grafted as in Stentor, and are 

 probably too small to permit this approach, by making suitable 

 incisions in single and dividing animals while keeping the parts 

 joined by the endoplasm, Suzuki was able to shift these parts with 

 reference to one another and produce a variety of alterations and 

 disarrangements closely paralleling several of those which have 

 been achieved in Stentor. Cutting and enucleation experiments 

 completed the study. Similarities in the performance of Blepharisma 

 and Stentor are so numerous that these correspondences might 

 have been referred to repeatedly throughout our discussions, but 

 I have chosen to review them together, since this will allow the 

 special comment which is called for as well as reflecting the 

 independence of these studies. 



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