96 



Regulation of Size in Unicellular Organisms 



nuclei. A nucleus alone may constitute five percent or 

 more of the body volume. It would be possible to re- 

 gard the presence of many, or multiple, or elongated, 

 nuclei in large unicellular species as conferring of it- 

 self a high capacity for regeneration. 



For technical reasons the large species of organisms 

 have alone been used to study the sizes of "minimal 

 reorganization masses". The absolute volumes of 

 these pieces are not small, therefore, as compared with 



Table 8. 

 Least Portions of Protozoa Which are Capable of Complete Regeneration 



species which are normally small. Moreover, in some 

 species there exist clones which are as diverse in size 

 as the volumes of these pieces and as the volumes of the 

 original organisms from which they were cut. In fact, 

 as will be shown later, starvation alone may reduce the 

 volumes of individuals in numerous species as much as 

 the cutting reduced these. 



Repeated cuttings appear (table 8) to result in re- 

 ductions which are viable in considerably smaller sizes. 

 But in none of the experiments performed is it clear 

 that cutting alone was responsible for the result, for 

 starvation prevailed, and perhaps other chemical fac- 

 tors were potent. 



The age factor. It has been concluded by some in- 

 vestigators that age of individuals is a factor in re- 



