-14 Heredity and Eugenics 



progeny be modified in the same manner, tliere are two 

 possible explanations. The incident conditions ma>' modify 

 both soma and germ independentl}', and they would be 

 similarh' modified because both soma and germ represent 

 one and the same group of potentialities; or the observed 

 results can be ex])laine(l by assuming that incident conditions 

 first modif>' the soma, and secondarily, through transmission, 

 tlie modification is incorporated into the germ cell; and 

 thus be interpreted as upholding the neo-Lamarckian idea 

 of the inheritance of accjuired soma variations. It follows, 

 therefore, that the germ cells upon which experiments are to 

 be carried out must either be taken from the body of the 

 parent and placed in indift'erent media before being experi- 

 mented upon, or they must be in organisms that can under- 

 go no further somatic modifications. In this there could, 

 of course, be no transmission of acquired variations, because 

 no \-ariations are acr[uired. ^Moreover, for our purpose 

 any resulting change must be thoroughly tested by subse- 

 quent breeding for many generations. 



When these organisms attain sexual maturity, they have 

 attained all of the somatic modifications, save pathological 

 growths, which it is possible for them to achieve; the onto- 

 genetic development of variations has come to a standstill, 

 the whole acti\'ity of the organism is directed to reproducing 

 the species, and further develo])ment or divergence in any 

 of its attributes or qualities is forever inhibited. Whatever 

 changes occur, from sexual maturity onward, are pathological 

 or senescent. 



It is possible, therefore, to eliminate from these experi- 

 ments the neo-Lamarckian factor, because the conditions 

 of experiment were not applied until after the parents had 



