VIII.] SUPPOSED TRANSMISSION OF MUTIIATIOXS. 44- 



In the same manner fourteen of the ofispring of tliis 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, tlicrc was not 

 a single one with an abnormal tail. Precisely the same result 

 occurred in the fourth generation, which were bred in a fourtli 

 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 genera- 

 tion ; 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 shorter than 10.5 mm. Furthermore 

 there was no difference in this respect between the young of 

 the earlier and later generations. 



What do these experiments prove ? Do they disprove once 

 for all the opinion that mutilations cannot be transmitted .' 

 Certainly not, when taken alone. If this conclusion were 

 drawn from these experiments alone and without considering 

 other facts, it might be rightly objected that the number of 

 generations had been far too small. It might be urged that it 

 was probable that the hereditary effects of mutilation would only 

 appear after a greater number of generations had elapsed. 

 They might not appear by the fifth generation, but perhaps 

 by the sixth, tenth, twentieth, or hundredth generation. 



We cannot say much against this objection, for there are 

 actual phenomena of variation which must depend upon such a 

 gradual and at first imperceptible change in the germ-plasm, a 

 change which does not become visible in the descendants until 

 after the lapse of generations. The wild pansy does not change 

 at once when planted in garden soil : at first it remains 

 apparently unchanged, but sooner or later in the course of 

 generations variations, chiefly in the colour and size of the 



