The Rate of Multiplication 77 



related, in Paramecium, where fully adequate environ- 

 mental influences were at first not identified, with in- 

 ternal structural reorganization processes 14 . But, in 

 most species, such reorganizations as involve the nu- 

 clei occur only in encysted or other non-vegetative 

 states of existence (Fermor, '13). In nearly all species 

 both the trends in rates of reproduction and the nu- 

 clear reorganizations have been found controllable, 

 and usually avoidable. 



3. Inhibition of Reproduction 



The possibility of separating reproduction from 

 growth in size, in unicellular organisms, has often been 

 suggested, but the experimental realization of it has 

 been surprisingly rare. 



Separation from growth. The greater or lesser size 

 of organisms which are cultivated under contrasting 

 conditions has frequently been measured. The modi- 

 fication of adult size by temperature means that the 

 ratio which reproduction bears to growth in volume 

 differs at each temperature. Jollos ('13) showed that 

 some inorganic substances also affected the size of 

 Paramecium in such a way that reproduction and 

 growth in size were influenced differently; therefore, 

 he concluded, the regulators of the two are not identi- 

 cal. 



Perhaps the clearest case of separation of reproduc- 

 tion from growth is that studied by Hartmann ('21) 

 in Eudorina. In this green colonial flagellate, under 

 certain conditions, the asexual reproduction of thirty- 

 two new colonies from one parent colony occurred 

 every fifth day, when light is supplied for twelve hours 

 out of each twenty-four. When, however, the same 

 light is supplied continuously, reproduction is has- 



" Woodruff and Erdmann ('14), Hertwig ('14), Erdmann and Woodruff 

 ('16), Jollos ('16), Woodruff ('17), Young ('17, '18). 



