94 HEREDITY [ch. 



prove 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 inherit- 

 ance 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-Sequard 

 on the inheritance 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 

 been confirmed there are other possible explanations 

 of the apparent transmission of the effects of injury. 

 For example, Brown-Sequard found that when the 

 chief nerve of the leg is severed, the toes become 



