710 REV. DR. GOODACRE ON THE CHINESE GOOSE. [Nov. 18, 



10. On the Question of the Identity of Species of the 

 Common Domestic and the Chinese Goose. By F. B. 

 Goodacre, M.D., F.Z.S. 



[Eeceived September 16, 1879.] 



Having read long ago, in 'The Origin of Species' (p. 275), about 

 the fertility inter se of " hybrids " between the Common Domestic 

 and Chinese Geese, I was induced, when the opportunity occurred 

 some few years ago, to commence a series of experiments to verify 

 this alleged fertility, several gentlemen very kindly consenting to 

 assist me in the investigation. The following crosses have been 

 obtained by one or another of us, and some of them in more than 

 one case : — Chinese S with Common $ produced several Goslings ; 

 a pair of these, out of the same nest, have produced young last 

 year and again this ; half-bred cf with both Common $ and Chi- 

 nese $ ; one quarter Chinese and three quarters Common <$ with 

 both Common $ and Chinese 5 . 



The number of the Goslings in proportion to that of the eggs 

 has been small in many, but not in all cases, and is, I think, to 

 be attributed to some accident in our arrangements, and not to 

 any lurking sterility between the two forms. In fact I suspect 

 the two forms themselves, and cross-bred birds of them in any pro- 

 portions, to be quite as fertile inter se as either of the pure forms 

 by itself. 



Now the chief interest in the results of these experiments seems 

 to be that half-bred birds of the same nest produced young ; for, 

 as a consequence of their doing so, we seem compelled to believe 

 one of two things, either that hybrid birds can be fertile inter se, 

 or that the half-bred birds above mentioned were not hybrids 

 at all, but only mongrels ; in other words, that the two forms of 

 Domestic Goose are specifically identical. Most naturalists have 

 hitherto considered them specifically distinct ; it is certain they 

 either are or are not ; and how is the case to be decided 1 The de- 

 claration of the most learned naturalists either way cannot settle the 

 point, nor do I see any way of doing so beyond all doubt if we give 

 up that rule, so generally received, that hybrids are infertile inter se, 

 and, of course, we cannot quote that rule as a proof against an ap- 

 parent exception to itself. Yet the fertility of these cross-bred birds 

 may be taken as good presumptive evidence in favour of identity of 

 species in their parent forms, and is quite sufficient to make us 

 inquire more curiously into the matter, to see what other evidence can 

 be found to incline us to believe in such identity. The advocates 

 of their non-identity would very naturally call our attention to the 

 great difference between them as to general form, colour, and voice, 

 to the peculiar knob on the Chinese bird's head, and to its prolonged 

 season of incubation. The existence of the last of these differences 

 (except in books) I have good reason to deny ; the other differences 

 must be admitted, and something said with reference to each to show 



