786 



MORPHOGENESIS 



parts from which they regenerate has been emphasized by Morgan 

 (1901), Sokoloff (1923), and Dembowska (1926). The latter noted 

 that even the most minute parts of a small Uronychia regenerate were of 

 proportionate size. The small regenerators retained none of the large, 

 original cirri. The new cirri developed from corresponding Anlagen 

 and grew only until proportionate size was attained. 



The quest for minimum reorganization volume in Protozoa originated 

 with those embryologists who were interested in the totipotency of 

 early blastomeres and gastrula fragments. Perhaps it has been partly 

 successful in demonstrating that a specific organization can be contained 



Table 21: Table of Minimum Volumes Necessary for Regeneration 



(Sokoloff, 1923) 



within bits of protoplasm much smaller than previously shown for 

 separated blastomeres, and that the disadvantages of small volumes for 

 the mechanical processes involved in cleavage, gastrulation, and so forth, 

 are not necessarily the reasons for developmental failure in small blasto- 

 meres. The knowledge that minute fractional parts of a protozoan are 

 capable of regenerating also has a practical value in experimental work. 

 The assignment of a certain experimentally determined value as either 

 the absolute or the relative minimal mass does not greatly enhance the 

 theoretical implications of these works. We learn that one fifty-third or 

 one eightieth of the protoplasm of a cell of a given species regenerates 

 under favorable conditions, but, as Lillie (1896) aptly remarked, this 



