134 DOCTRINE OF EVOLUTION 



then begin, not where their parents did, but from an 

 advanced condition. Thus, by continued stretching 

 of the neck and by continued transmission of the 

 elongated condition, the great length of this part of 

 the body in the modern giraffe would be attained. 



The explanation of natural selection would be quite 

 different. The Darwinian would say that all the young 

 giraffes of any one generation would vary with respect 

 to the length of the neck. Those with longer necks 

 would have a slight advantage over their fellows in 

 the extended sphere of their grazing territory. Being 

 better nourished than the others, they would be stronger 

 and so they would be more able to escape from their 

 flesh-eating foes, like the lion. For the reason that their 

 variation would be congenital and therefore already 

 transmissible, their offspring would vary about the ad- 

 vanced condition, and further selection of the longer 

 necked individuals would lead to the modern result. 



The Lamarckian explanation encounters one grave 

 difficulty which is not met by the second one, in so far 

 as it demands some method by which a bodily change 

 may be introduced into the stream of inheritance. 

 So far, this difficulty has not been overcome, and the 

 present verdict of science is that the transmission of 

 characters acquired as the result of other than congenital 

 factors is not proved. It would be unscientific to say 

 that it cannot be proved in the future, but there are good 

 a priori grounds for disbelief in the principle, while 

 furthermore the results of experiments that have been 

 undertaken to test its truth have been entirely negative. 

 Rats and mice have had their tails cut off to see if this 

 mutilation would have its effect upon their young, and 



