444 SUPPOSED TRANSMISSION OF MUTILATIONS. [VIII. 



ment : 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 rudimentary 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 

 begun in October of last year (1887), with seven females 

 and five males. On October 17 all their tails were cut off, and 

 on November 16 the two first families were born. Inasmuch as 

 the period of pregnancy is only 22-24 days, these first offspring 

 began to develope at a time when both parents were without 

 tails. These two families were together eighteen in number, 

 and every individual possessed a perfectly normal tail, with a 

 length of ii-i2mm. These young mice, like all those born at 

 later periods, w^ere removed from the cage, and either killed 

 and preserved, or made use of for the continuance of the 

 breeding experiments. In the first cage, containing the twelve 

 mice of the first generation, 333 young were born in fourteen 

 months, viz. until January 16, 1889^ and no one of these had a 

 rudimentary tail or even a tail but slightly shorter than that of 

 the offspring of unmutilated parents. 



It might be urged that the effects of mutilation do not 

 exercise any influence until after several generations. I 

 therefore removed fifteen young, born on December 2, 1887, 

 to a second cage, just after they were able to see, and were 

 covered with hair ; their tails were cut off. These mice 

 produced 237 young from December 2, 1887, to January 16, 

 1889, every one of which possessed a normal tail. 



