7 an. r, 1880] 



NATURE 



207 



FERTILITY OF HYBRIDS FROM THE 

 COMMON AND CHINESE GOOSE 



IN the " Origin of Species " I have given the case, on 

 the excellent authority of Mr. Eyton, of hybrids 

 from the common and Chinese goose (Anser cygnoides) 

 being quite fertile inter se ; and this is the most remark- 

 able fact as yet recorded with respect to the fertility of 

 hybrids, for many persons feel sceptical about the hare 

 and the rabbit. I was therefore glad to have the oppor- 

 tunity of repeating the trial, through the kindness of the 

 Rev. Dr. Goodacre, who gave me a brother and sister 

 hybrid from the same hatch. A union between these 

 birds was therefore a shade closer than that made by Mr. 

 Eyton, who coupled a brother and sister from different 

 hatches. As there were tame geese at a neighbouring 

 farm-house, and as my birds were apt to wander, they were 

 confined in a large cage ; but we found out after a time 

 that a daily visit to a pond (during which time they were 

 watched) was indispensable for the fertilisation of the 

 eggs. The result was that three birds were hatched from 

 the first set of eggs ; two others were fully formed, but 

 did not succeed in breaking through the shell; and the 

 remaining first-laid eggs were unfertilised. From a 

 second lot of eggs two birds were hatched. I should 

 have thought that this small number of only five birds 

 reared alive indicated some degree of infertility in the 

 parents, had not Mr. Eyton reared eight hybrids from 

 one set of eggs. My small success may perhaps be attri- 

 buted in part to the confinement of the parents and their 

 very close relationship. The five hybrids, grandchildren 

 of the pure parents, were extremely fine birds, and re- 

 sembled in every detail their hybrid parents. It ap- 

 peared superfluous to test the fertility of these hybrids 

 with either pure species, as this had been done by Dr. 

 Goodacre ; and every possible gradation between them 

 may be commonly seen, according to Mr. Blyth and 

 Capt. Hutton in India, and occasionally in England. 



The fact of these two species of geese breeding so 

 freely together is remarkable from their distinctness, 

 which has led some ornithologists to place them in sepa- 

 rate genera or sub-genera. The Chinese goose differs 

 conspicuously from the common goose in the knob at the 

 base of the beak, which affects the shape of the skull ; in 

 the very long neck with a stripe of dark feathers running 

 down it ; in the number of the sacral vertebras ; in the 

 proportions of the sternum ; * markedly in the voice or 

 "resonant trumpeting," and, according to Mr. Dixon," in 

 the period of incubation, though this has been denied by 

 ■others. In the wild state the two species inhabit different 

 regions. 3 I am aware that Dr. Goodacre is inclined to 

 believe that Anser cygnoides is only a variety of the com- 

 mon goose raised under domestication. He shows that 

 in all the above indicated characters, parallel or almost 

 parallel variations have arisen with other animals under 

 •domestication. But it would, I believe, be quite impos- 

 sible to find so many concurrent and constant points of 

 difference as the above, between any two domesticated 

 varieties of the same species. If these two species are 

 classed as varieties, so might the horse and ass, or the 

 hare and rabbit. 



The fertility of the hybrids in the present case probably 

 ■depends to a limited degree (i) on the reproductive power 

 of all the Anatidae being very little affected by changed 

 conditions, and (2) on both species having been long 

 domesticated. For the view propounded by Pallas, that 

 domestication tends to eliminate the almost universal 

 sterility of species when intercrossed, becomes the more 

 probable the more we learn about the history and multiple 

 origin of most of our domesticated animals. This view, 



1 Charlesworth's " Mag. of Nat. Hist.," vol. iv., new series, 1840. p. go. 

 T. C. Eyton, "Remarks on the Skeletons of the Common and Chinese 

 Goose." 



3 " Ornamental and Domestic Poultry," 1848, p. 85. 



3 Dr. L. v. Schrenck's " Reiscn und Forschungen im Amur-Land,' B. i. 

 P- 457- 



in so far as it can be trusted, removes a difficulty in the 

 acceptance of the descent-theory, for it shows that mutual 

 sterility is no safe and immutable criterion of specific 

 difference. We have, however, much better evidence on 

 this head, in the fact of two individuals of the same form 

 of heterostyled plants, which belong to the same species 

 as certainly as do two individuals of any species, yielding 

 when crossed fewer seeds than the normal number, and 

 the plants raised from such seeds being, in the case of 

 Lythium sa/icaria,as sterile as are the most sterile hybrids. 

 Down, December 15 Charles Darwin 



CL OUD CLA SSIFICA TION ' 

 '"THE work of a meteorologist who has devoted himself 

 ■*• with great diligence for many years to the study of the 

 structure, forms, and movements of the clouds, possesses 

 a strong claim on the attention of all who are interested 

 in this difficult branch of science. Independently of the 

 importance of the challenge which Prof. Poey offers 

 to an existing system of nomenclature, his book contains 

 numerous facts and suggestions of very considerable 

 scientific value. In the present enlarged and revised 

 edition the author has endeavoured to satisfy the require- 

 ments of our advancing knowledge on the subject of 

 which he treats ; a task which ought, unfortunately, to be 

 one of no great difficulty, owing to the small amount 

 of progress which has been made in this, as compared 

 with other departments of meteorology, since the appear- 

 ance of the second edition. 



The history of cloud-nomenclature has been to a great 

 extent a record of wrecks and casualties, because classifi- 

 cation has, by an unfortunate necessity, preceded the 

 knowledge of the physical structure of the objects 

 classified. Prof. Poey was one of the first to appreciate 

 the importance of the fact that the terminology of the 

 clouds must, ultimately, be based not simply upon the 

 varieties of the forms of clouds, but upon those physical 

 conditions to which these varieties are related. But our 

 knowledge of the physical conditions which determine the 

 development of the modifications of cloud is at the 

 present time so limited that no classification founded 

 thereon can as yet be unreservedly adopted. A great deal 

 of questionable hypothesis necessarily enters into the 

 construction of Prof. Poe'j's scheme, as he would, we 

 believe, with the candour which distinguishes him, be the 

 first to admit. There is of course a strong prima facie 

 desirability that cloud observers should possess some 

 definite system of nomenclature ; and at present nearly 

 all of them, not of the lazy class, complain that cloud- 

 classification is still in a state of chaos. Yet it maybe 

 doubted whether, for some years to come, a Meteorological 

 Congress will be able to establish an absolutely fixed 

 system of classification which will be universally accepted. 

 Of the ground on which such a system should be built 

 science has hitherto explored but a small portion : and 

 even where we have the materials for observational and 

 experimental research in this direction, very inadequate 

 use has been made of these materials. The immediately 

 practical problem which is raised by the study of this 

 book is this : — In the provisional adaptation of our cloud 

 classification to the status of our knowledge, is it desirable 

 that Prof. Poey's terminology be adopted in lieu of 

 that of Howard, or should the still prevailing nomenclature 

 be retained, with such modifications as the observations 

 of Poey and of other students of the subject have as yet 

 shown to be necessary ? To this problem we shall venture 

 in the present article to suggest an answer. 



As might be expected from the condition of the subject 

 the critical portion of Prof. Poey's treatise is more 

 successful than the constructive. Several of Howard s 

 terms have had from the first an ill-fated career. To 



■ "Comment on observe les Nuages pour prevoir le Temps." Par Andre 

 Poey. Third Edition. (Paris : Gautruer-\ il.ars, 1S79.) 



