230 



The Journal of Heredity 



As concerns swine, Darwin also cites 

 a lonj^^ list of English witnesses, part of 

 whom had written on the subject, and 

 part of whom had given him their views 

 orally. "With respect to pigs," Darwin 

 says, "there is more unanimity amongst 

 breeders on the evil effects of inter- 

 breeding than, perha])s, with any other 

 large animal. Air. Drucc, a great and 

 successful l)recder of the Improved 

 Oxford.shires (a crossed race), writes, 

 'without a change of boars of a different 

 tribe, but of the same breed, constitution 

 can not be preserved.' Mr. Fisher 

 Hobbs, the raiser of the celebrated 

 Improved Essex breed, divided his 

 stock into three separate families, by 

 which means he maintained the breed 

 for more than 20 years, 'by judicious 

 selection from the tliree distinct families.' 

 Lord Western was the first importer of 

 a Neapolitan boar and sow. 'From this 

 pair he bred in-and-in, until the breed 

 was in danger of becoming extinct, a 

 sure result fas Mr. vSidney remarks) of 

 inbreeding.' Lord Western then crossed 

 his Neapolitan pigs with the old Essex 

 and made the first great step toward 

 the Im]5roved Essex breed. 



A REMARKABLE CASE. 



"Here is a more interesting case. 

 Mr. J. Wright, well-known as a breeder, 

 crossed the same boar with the daugh- 

 ter, granddaughter, great-granddaughter, 

 and so on for seven generations. The 

 result was that in many instances the 

 offspring failed to breed; in others they 

 produced few that lived; and of the 

 latter many were idiotic, without sense, 

 even to suck, and when attempting to 

 moYC could not walk straight. Now it 

 deserves especial notice, that the two 

 last sows ])roduced by this long course 

 of interbreeding were sent to other 

 boars, and they bore several litters of 

 healthy pigs. The best sow in external 

 appearance produced during the whole 

 seven generations was one in the last 

 stage of descent ; but the litter consisted 

 of this one sow. She would not breed 

 to her sire, yet bred at the first trial to a 

 stranger in l)lood. So that, in Mr. 

 Wright's case, long-continued and ex- 

 tremely close interbreeding did not 

 affect the general form or mcril of the 



young; but with many of th?m the 

 general constitution and mental powers, 

 and especially the reproducti\'e func- 

 tions, were seriously affected." 



With regard to dogs an attempt has 

 often been made to show that inbreeding 

 has no influence, according to Darwin, 

 Mcyncll's famous foxhounds, for ex- 

 ample, being cited as having l^een bred 

 closely in-and-in without the least trace 

 of injury Vjcing discernible. J. Sebright, 

 however, declares that he had seen "the 

 offspring of strong spaniels degenerate 

 into weak and diminutive lapdogs," as 

 a result of the pairing of brother and 

 sister. And W. D. Fox noted that with 

 consanguineous brssding of blood- 

 hounds a visible degeneracy took place, 

 and that almost all the animals had an 

 enlargement of the bones of the tail. 

 A single crossing with foreign blood- 

 hounds restored their fecundity and 

 drove away the tendency to malforma- 

 tion in the tail. "Considering how 

 rapid is the natural increase of the dog," 

 Darwin reflects, "it is difficult to under- 

 stand the large price of all highly im- 

 proved breeds, which almost im]jlies 

 long-continued close interbreeding, 

 except on the belief that this process 

 lessens fertility and increases liability 

 to distemper and other diseases." 



DATA FROM FOWLS. 



Of the greatest im])ortance for the 

 question of inbreeding arc. Anally, the 

 authorities gathered by Darwin relating 

 to the breeding of fowls. According to 

 Sebright's stitsm^nts his bantams be- 

 came almost infertile through inbreed- 

 ing, and the cocks, losing the secondary 

 sexual characters, approached a female 

 type; but the slightest degree of rever- 

 sion to the ]jroper male type — for 

 exam]jle, the elongation of the two 

 ])rincipal tail feathers by only half an 

 inch, l)rought with it "an improved 

 probability of increased fertility." 



According to Wright's testimony Mr. 

 Clark's fighting-cocks were so much 

 affected by ]jrolongcd inbreeding that 

 they allowed themseh'cs to be knocked 

 over withovit .showing fight. Their 

 weight decreased, to the great injury of 

 their prize-winning power. Through a 

 crossing with Mr. Leighlon's stock, 



