THE SUPPOSED TRANSMISSION OF MUTILATIONS. 431 



sexual selection, for the latter also works upon such functionally 

 indifferent but striking 1 variations. In the case of the cats, man 

 has favoured a particular variation, because the novelty rather than 

 the beauty of the character surprised and attracted him. He has 

 attached an imaginary value to the new character, and by arti- 

 ficial selection has helped it to predominate over the normal form. 

 I see no reason why the same process should not take place in 

 animals by the operation of sexual selection. 



But now, after this little digression, let us return to the trans- 

 mission of mutilations. 



We have seen that the rudimentary tails of cats and dogs, as far 

 as they can be submitted to scientific investigation, do not depend 

 upon the transmission of artificial mutilation, but upon the spon- 

 taneous appearance of degeneration in the vertebral column of the 

 tail. The opinion may, however, be still held that the customary 

 artificial mutilation of the tail, in many races of dogs and cats, has 

 at least produced a number of rudimentary tails, although, perhaps, 

 not all of them. It might be maintained that the fact of the 

 spontaneous appearance of rudimentary tails does not disprove the 

 supposition that the character may also depend upon the trans- 

 mission of artificial mutilation. 



Obviously, such a question can only be decided by experiment : 

 not, of course, experiments upon dogs and cats, as Bonnet rightly 

 remarks, but experiments upon animals the tails of which are not 

 already in a process of reduction. Bonnet proposes that the 

 question should be investigated in white rats or mice, in which the 

 length of the tail is very uniform, and the occurrence of rudi- 

 mentary tails is unknown. 



Before this suggestion was made, I had already attacked the 

 problem experimentally. Such a course might, perhaps, have been 

 more natural to those who maintain the transmission of mutilations, 

 to which I am opposed. Although I undertook the experiments 

 expecting to obtain purely negative results, I thought that the 

 latter would not be entirely valueless ; and since the numerous 

 supporters of the transmission of acquired characters do not seem to 

 be willing to test their opinion experimentally, I have undertaken 

 the not very large amount of trouble which is necessary in order to 

 conduct such an experimental test. 



The experiments were conducted upon white mice, and were 



