230 



an effect of non-genetic factors is possible because of the experi- 

 ments of Tower. But in such a case it is very improbable that 

 the falling-out of a genetic factor should produce an effect on 

 the taillength rather than on the colour or on the form of the 

 animal's humerus or anything eise. 



It is very far from probable that the mice, whose taillength 

 is modified by Przibram by subjecting them before or after birth 

 to a different temperature, will produce offspring with longer 

 tails than normal mice, on condition that these young will not 

 themselves be either before or after birth subjected to the changed 

 non-genetic factors for taillength. Hitherto the alleged cases of 

 the inheritance of modifications are all based on a play of words, 

 reckoning the new generation to begin at birth, instead of at 

 the formation of the Zygote, so that the effects of non-genetic 

 factors on an unborn individual can be attributed to the modifi- 

 cations of its mother. A beautifull example of this is seen in 

 the recent experiments of Kammer er. He found that a certain 

 lizard, in a high temperature changed the white colour of its 

 abdomen into red. He found that the young born from such a 

 lizard had the colour of their mother. When this was red through 

 high temperature, the young born were red, when the mother 

 had lost its red colour after being brought back into a lower 

 temperature, the young born were normal. He now found, that 

 when he brought back the mother to a low temperature before 

 the birth of the young, these young, when born sufficiently early 

 after the change of temperature, were still red. He concludes 

 from these facts that the effect of the temperature is transmitted. 

 In a certain sense it is, for, as the young are inclosed in the 

 body of the mother, they can only receive the additional heat 

 through the intermediary of the tissues of the heated mother. 

 Of course it is wordplay to call such a process by the name of 

 heredity. One could as well say, that, as the offspring of heated 

 lizards are born hot in a high temperature, this temperature was 

 inherited. The fact that the young lizards, born after the mother 

 has had time to cool off are born cold but still redbellied only 

 shows that the red colour resulting from a hot environment 

 persists longer than the body-temperature itself. 



As to the development of each individual of a strain coope- 

 rate about the same set of non-genetic factors, and as the 

 reaction of the development on these factors is always essentially 



