94 HEREDITY [CH. 



the inherited effects of conditions is the experiment 

 of Kellogg in starving silkworms, in which he found 

 that when the caterpillars were starved for two 

 generations, the third generation, even if well fed, 

 were below the normal size. But there is here a 

 possible source of error, that the eggs produced by 

 starved females may have been lacking in yolk, so 

 that the resulting caterpillars would be weakly from 

 the beginning and never overtake the normal size. 

 If so, the apparent effect of inheritance of bad 

 conditions would be due really to poor embryonic 

 nourishment, not to germinal difference. The same 

 explanation might apply to the apparent cumulative 

 effects of under-feeding in man, if the mother cannot 

 adequately nourish the infant before birth. The 

 famous experiments of Brown-S^quard on the in- 

 heritance of artificial injuries in guinea-pigs must 

 be mentioned. He found that when the parents 

 were subjected to operations of various kinds, some 

 of the young showed corresponding abnormalities, 

 especially in the case of the effects of certain injuries 

 to the nervous system. Subsequent experiments 

 however have not completely confirmed his results, 

 and there is reason to believe that where they have 



Arctia caja, definite evidence for the transmission of modifications 

 was obtained, but this may have been due to direct modification of 

 the germ-cells themselves. 



