66 THE EVOLUTION THEORY 



the slightest diminution in the length of tail in the descendants. 

 I have myself instituted experiments of this kind, and carried them 

 out through twenty-two successive generations, without any positive 

 result. Corroborative results of these experiments on mice have been 

 communicated by Ritzema Bos and, independently, by Rosenthal, 

 and a corresponding series of experiments on rats, which these two 

 investigators carried out, yielded the same negative results. 



When we remember that all the cases which have been brought 

 forward in support of an inheritance of mutilations refer to a single 

 injury to one parent, while, in the experiments, the same mutilation 

 was inflicted on both parents through numerous generations, we must 

 regard these experiments as a proof that all earlier statements w^ere 

 based either on a fallacy or on fortuitous coincidence. This con- 

 clusion is confirmed by all that we know otherwise of the effects of 

 oft-repeated mutilations, as for instance the well-known mutilations 

 and distortions which many peoples have practised for long, sometimes 

 inconceivably long, ages on their children, especially circumcision, the 

 breaking of the incisors, the boring of holes in lip, ear, or nose, and 

 so forth. No child of any of these races has ever been brought 

 into the world with one of these marks ; they have to be re-impressed 

 on every generation. 



The experience of breeders agrees with this, and they therefore, 

 as Wilckens remarks, have long regarded the non-inheritance of 

 mutilations as an established fact. Thus there are breeds of sheep in 

 which, for purely practical reasons, the tails have been curtailed quite 

 regularly for about a century (Kuhn) ; but no sheep with a stump-tail 

 has ever been born in this breed. This is all the more important 

 because there are other breeds of sheep (fat-rumped sheep) in which 

 the lack of the tail is a breed character ; it is thus not the case that 

 there is anything in the intrinsic nature of the tail of the sheep to 

 prevent it becoming rudimentary. The artificially rounded ear of 

 fox-terriers, too, though cut for generations, never occurs hereditarily, 

 Mr. Postans of Eastbourne informs me that the cocks which are to be 

 used for cock-fighting are docked of their combs and wattles before- 

 hand, and that this had been done for at least a century, but that no 

 fighting cock without comb and wattles has been reared. In the 

 same way various breeds of dog, such as the spaniels, have had their 

 tails cut to half their length regularly and in both sexes for more 

 than a century, yet in this case there is no hereditary diminution of 

 the length of tail. Deformed stump-tails do indeed occur in most 

 breeds of dog, but, as I said before, their anatomical character is quite 

 different from that of artificially shortened tails, moreover they may 



