174 



K. S. LASHLEY 



7.0 



6.5 



6,0 



tentacles 



J JL 



10 



15 



Successive buds 



Fig. 3 The mean number of tentacles of the successive buds produced by 



polyps after regeneration; ( ) buds produced by regenerated oral ends; ( ) 



buds produced by regenerated aboral ends; all polyps were taken from the same 

 clone. 



Temperatures much above or below the optimum have an effect 

 hke that of high salt content. The results of the action of these 

 agents resemble the cases of temporary parallel induction found 

 in parthenogenetic reproduction (Agar '13) but the mechanism 

 of the action is probably much simpler since we are dealing here 

 only with a congenital reduction in vigor. 



III. EXISTENCE OF DIVERSE RACES 



In addition to these variations resulting from environmental 

 action, are there differences between the individuals of a popu- 

 lation due to some internal, hereditary factors? This question 

 has been tested by breeding a number of clones of H. viridis 

 under similar cultural conditions. 



