162 DARWINISM chap. 



sucli thing as " perfect health " in man, and probably no such 

 thing as absolute freedom from constitutional taint in animals. 

 The experiments of Mr. Darwin, sho^^ang the great and 

 immediate good effects of a cross between distinct strains in 

 plants, cannot be explained away ; neither can the innumerable 

 arrangements to seciu'e cross-fertilisation by insects, the real 

 use and purport of which will be discussed in our eleventh 

 / chapter. On the Avhole, then, the evidence at our command 

 ' proves that, Avhatever may be its ultimate cause, close inter- 

 breeding does usually produce bad results ; and it is only by 

 the most rigid selection, Avhether natui'al or artificial, that 

 ' the danger can be altogether ob^^ated. 



Fertile Hyhrids among Animals. 



One or two more cases of fertile hybrids may be given 

 before we pass on to the corresponding experiments in plants. 

 Professor Alfred Newton received from a friend a pair of 

 hybrid ducks, bred from a common duck (Anas boschas), and a 

 pintail (Dafila acuta). From these he obtained four ducklings, 

 but these latter, when grown up, proved infertile, and did not 

 breed again. In this case Ave have the results of close inter- 

 breeding, ^Yiih. too gi'eat a difference between the original 

 species, combining to produce infertility, yet the fact of a 

 hybrid from such a pair producing healthy offspring is itself 

 noteworthy. 



Still more extraordinary is the following statement of Mr. 

 Low : "It has been long known to shepherds, though ques- 

 tioned by naturalists, that the progeny of the cross between the 

 sheep and goat is fertile. Breeds of this mixed race are 

 numerous in the north of Europe." ^ Nothing appears to be 

 known of such hybrids either in Scandina-vda or in Italy ; but 

 Professor Giglioli of Florence has kindly given me some useful 

 references to works in which they are described. The follo's^'ing 

 extract from his letter is very interesting : " I need not tell 

 you that there being such hybrids is now generally accepted as 

 a fact. Bufton {Supplements, tom. iii. p. 7, 1756) obtained one 

 such hybrid in 1751 and eight in 1752. Sanson {La Cidhire, 

 vol. \\. p. 372, 1865) mentions a case observed in the Yosges, 

 France. Geoff. St. Hilaire {Hist. Nat. G6n. desreg. org., vol. iii. p. 

 •^ Low"s Domesticated Animals, 'p. 28. 



