LESSONS OF EVOLUTION 609 



stimuli, which are to our potentialities as sunshine and rain 

 to buds. " As is the world on the banks, so is the mind 

 of man." " What we have inherited from our ancestors 

 we must put to use, if it is to become our very own." When 

 a belief in the transmission of individually acquired somatic 

 modifications was general, reformers tended to exaggerate 

 the directly ameliorative value of good nurture. Now that 

 the belief in the transmission of individually acquired modi- 

 fications has been badly shaken, many thinkers have swung 

 to the opposite extreme, and the role of nurture is depreciated. 

 But its individual importance remains, and its indirect im- 

 portance also. 



Prof. Karl Pearson and his collaborators have con- 

 cluded that " the degree of dependence of the child on the 

 characters of its parentage is ten times as intense as its de- 

 gree of dependence on the character of its home or uprear- 

 ing ". " It is five to ten times as profitable for a child to be 

 born of parents of sound physique and of brisk, orderly men- 

 tality, as for a child to be born and nurtured in a good physi- 

 cal environment." It may be doubted, however, whether it is 

 possible to discriminate so precisely between what is due to 

 hereditary nature and what is due to available nurture. It 

 is also important to inquire when the nurture is supposed 

 to begin: there is much nurture before birth. 



Since hereditary nature and liberating nurture are both 

 essential, there is no rigid antithesis. Nurture is im- 

 portant as a condition of normal development, and on the 

 richness of its liberating stimuli the degree of development 

 in part depends. 



Gudernatsch has shown that in tadpoles fed on thyroid 

 gland there is differentiation without growth, while in tad- 

 poles fed on thymus and spleen there is growth without 



