432 THE SUPPOSED TRANSMISSION OF MUTILATIONS. 



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

 males. On October 17 all their tails were cut off, and on Novem- 

 ber 1 6 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 in- 

 dividual possessed a perfectly normal tail, with a length of n- 

 12 mm. These young mice, like all those born at later periods, 

 were 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. 



In the same manner fourteen of the offspring of this second 

 generation were put in cage No. 3 on May i, 1888, and their 

 tails were also cut off. Among their young, 152 in number, 

 which had been produced by January 16, there was not a single 

 one with an abnormal tail. Precisely the same result occurred in 

 the fourth generation, which were bred in a fourth cage and treated 

 in exactly the same manner. This generation produced 138 young 

 with normal tails from April 23 to January 16. 



The experiment was not concluded with the fourth generation ; 

 thirteen mice of the fifth generation were again isolated and their 

 tails were amputated; by January 16, 1889 they had produced 41 

 young. 



Thus 901 young were produced by five generations of artificially 

 mutilated parents, and yet there was not a single example of a 

 rudimentary tail or of any other abnormity in this organ. Exact 

 measurement proved that there was not even a slight diminution 

 in length. The tail of a newly-born mouse varies from 10-5 to 

 12 mm. in length, and not one of the offspring possessed a tail 



