446 SUPPOSED TRANSMISSION OF MUTILATIONS. [VIII. 



flowers, begin to appear : these are propagated by seed and 

 are therefore the consequence of variations in the germ. The 

 fact that such variations never occur in the first generation 

 proves that they must be prepared for b}'' a gradual trans- 

 formation of the germ-plasm. 



It is therefore possible to imagine that the modifying effects 

 of external influences upon the germ-plasm may be gradual 

 and may increase in the course of generations, so that visible 

 changes in the body (soma) are not produced until the effects 

 have reached a certain intensity. 



Thus no conclusive theoretical objections can be brought 

 forward against the supposition that the hereditary trans- 

 mission of mutilations requires (e.g.) 1000 generations before it 

 can become visible. We cannot estimate a priori the strength 

 of the influences which are capable of changing the germ- 

 plasm, and experience alone can teach us the number of 

 generations through which they must act before visible effects 

 are produced. 



If therefore mutilations really act upon the germ-plasm 

 as the causes of variation, the possibility or even probability 

 of the ultimate appearance of hereditary effects could not be 

 denied. 



Hence the experiments on mice, when taken alone, do not 

 constitute a complete disproof of such a supposition : they 

 would have to be continued to infinity before we could main- 

 tain with certainty that hereditary transmission cannot take 

 place. But it must be remembered that all the so-called proofs 

 which have hitherto been brought forward in favour of the 

 transmission of mutilations assert the transmission of a single 

 mutilation which at once became visible in the following 

 generation. Furthermore the mutilation was only inflicted 

 upon one of the parents, not upon both, as in my experiments 

 with mice. Hence, contrasted with these experiments, all 

 such ' proofs ' collapse ; they must all depend upon error. 



It is for this reason important to consider those cases of 

 habitual mutilation which have been continually repeated for 

 numerous generations of men, and have not produced any 

 hereditary consequences. With regard to the habitually 

 amputated tails of cats and dogs I have already shown that 

 there is only an apparently hereditary effect. Furthermore, 



