Heredity and the Origin of Variations. 167 



of life. If each plastic embryo is moulded in turn by 

 similar influence, how can we conclusivly prove hereditary 

 summation ? Take a case that has been quoted in support 

 of hereditary modification. Greyhounds transported from 

 England to the uplands of Mexico are unable to course, 

 owing to the rarity of the atmosphere. Their pups are, 

 however, able to run down the fleetest hares without 

 difficulty. Now, this may be due to the fact that the dogs 

 acquire a certain amount of accommodation to a rare 

 atmosphere, and hand on their acquired power to their 

 offspring, which carry it on towards perfection. But it 

 may also be due to the fact that the pups, subject from the 

 moment of birth to the conditions of a rarified atmosphere, 

 are developed in accordance with these conditions. 



Or take another case that has been brought forward. 

 English dogs are known in hot climates, like that of India, 

 to degenerate in a few generations. Let us suppose that 

 these degenerate dogs are removed back to England, and 

 that their pups, born in English air and in our temperate 

 climate, are still degenerate : would not this, it may be 

 asked, show that the influence of climate on the body is 

 inherited ? I do not think that such a case would be 

 convincing. For the climate might well influence the 

 germ through the body. The body being unhealthy and 

 degenerate, the germ-cells must, one may suppose, suffer 

 too. The degenerate pup born in England might well owe 

 its degeneracy to effects wrought upon the germinal cells. 

 In other words, such a case would indicate some general 

 influence of the environment (including the environing 

 body) on the germ. It does not convince us that particular 

 modifications of body-cells as such are transmitted under 

 normal and healthy conditions. 



On the whole, it seems to me that the evidence we at 

 present possess on this head is not convincing or conclu- 

 sive in favour of the effects on the body alone being 

 transmitted to offspring. If cases can be brought forward 

 in which there can be no direct influence on the germ, in 

 which elimination is practically excluded, and in which 



