162 
DARWINISM 
CHAP. 
such thing as “ perfect health ” in man, and probably no such 
thinsr as absolute freedom from constitutional taint in animals. 
The experiments of Mr. Darwin, showing the great and 
immediate good effects of a cross between distinct strains in 
plants, cannot be explained away ; neither can the innumerable 
arrangements to secure cross-fertilisation by insects, the real 
use and purport of which will be discussed in our eleventh 
chapter. On the whole, then, the evidence at our command 
proves that, whatever may be its ultimate cause, close inter¬ 
breeding does usually produce bad results; and it is only by 
the most rigid selection, whether natural or artificial, that 
the danger can be altogether obviated. 
Fertile Hybrids 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 we have the results of close inter¬ 
breeding, with too great 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 cpies- 
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.” 1 Nothing appears to be 
known of such hybrids either in Scandinavia or in Italy; but 
Professor Giglioli of Florence has kindly given me some useful 
references to works in which they are described. The following 
extract from his letter is very interesting: “ I need not tell 
you that there being such hybrids is now generally accepted as 
a fact. Buffon ( Supplements , tom. iii. p. 7, 175G) obtained one 
such hybrid in 1751 and eight in 1752. Sanson {La Culture , 
vol. vi. p. 372, 18G5) mentions a case observed in the Vosges, 
France. Geoff'. St. Hilaire {Hist. Nat. Gin. des reg. org., vol. iii. p. 
1 Low’s Domesticated Animals, p. 28. 
