134 Controversial Questions. 



investigation may succeed in isolating the individual 

 factors of the environment as they affect the organism, 

 but at present we must be content with treating them to- 

 gether, as one plienomenon. 



It is simply impossible to draw any distinction be- 

 tween these nutritional modifications and individual varia- 

 tions in the strictest sense of the term. There seems to 

 be every stage in the transition from a state of affairs 

 in which the effect of external conditions is easily trace- 

 able as in the case of nutritional modifications, to one in 

 which the very reverse is the case. But this condition 

 of things is only apparent, for the more closely we go 

 into the matter the more evident does it become that the 

 changes of this kind (individual variations) are corre- 

 lated with changes in the environment. 



In horticulture it is well known that favorable and 

 highly altered conditions lead to the accumulation and 

 multiplication of individual differences whilst ordinary 

 and uniform conditions tend to dissipate them and to re- 

 duce all the individuals to the same level. ^ 



It is also well known that weedy specimens by no 

 means lack the characters of the variety to which they 

 belong but that they are simply nnnus-y 3.vmnts in fluc- 

 tuating variability. 



More accurate investigation will, doubtless, bring out 

 the identity of true individual variations with nutritional 

 modifications. Mac Leod has conducted some very in- 

 structive experiments in this connection. He compared 

 the number of marginal florets on well-grown and starved 

 specimens of the common cornflower (Centaurea Cyaniis) 

 and found that there was a very high positive correlation 

 between number and vigor. The stronger the plant the 



' Intracellulare Pangenesis, p. 30. 



