The Rate of Multiplication 83 



Under mechanical factors. Among rhizopods there 

 are reports of inhibition of reproduction, in the pres- 

 ence of certain mechanical conditions 15 . Levy ('24) 

 believed that separation at fission in Ameba proteus 

 was successfully prevented by confining the dividing 

 individual in a very small lane of water upon a slide 

 or by applying an appropriate mechanical stimulus. 

 Belar ('21) found the viscosity of agar medium a de- 

 termining factor in the separation of the progeny in 

 various species of Chlamydophrys. 



Unequal or eccentric fissions can be produced by a 

 number of different influences. Such were noted by 

 Ryder ('93b) in Euglena which were kept for some 

 days under a coverslip. He attributed the inequality 

 in mitosis to the localized shortage of oxygen in the 

 body, a conception which was supported by the addi- 

 tional fact that sister individuals which were lying side 

 by side became mature for fission at widely diverse 

 times. 



Centrifuging of Stentor was found by Popoff ('09) 

 to lead to subsequent unequal fissions. The inequali- 

 ties persisted for at least one week, during which a 

 fission occurred. The evidence is that such a modifica- 

 tion was ultimately restored to normal size (Burn- 

 side, '29). 



Popoff ('09) also tried the effect of cold, and stated 

 that some unequal progeny resulted. It is not clear 

 that such giants would persist when restored to the 

 original conditions of culture. It seems only inevitable 

 that more than one generation should be required for 

 complete restoration of size. 



Multiplication of nuclei only. The fates of individ- 

 uals in which cytoplasmic division failed to accompany 

 nuclear fission are various. Usually, it may be said, 



"Blochmann ('88), Stole ('06, '10), Kiihn ('16, '20), Levy ('24), Breuer 

 ('17), Belar ('21). 



