256 The Progress of Zoology. 



understood to be a month, that of the wild rabbit three weeks ; 

 the young of the rabbit are born blind, those of the hare see ; 

 the rabbit burrows, the hare seldom goes to earth. There is 

 one great peculiarity of these hybrids of very great importance 

 as to the question at issue — the males show a great disinclina- 

 tion to copulation, which is very different to the males of the 

 (so-called) species, and if we were to suppose such a cross to 

 arise in nature, we must also suppose it would soon be lost 

 through this very peculiarity. But much more interesting cases 

 bearing on the same question were communicated by Dr. Crisp, 

 in the paper from which we have gathered the above particu- 

 lars.* Four hybrid ducks were bred at the Zoological Gardens 

 between the summer duck (Anassponsa), the pochard (Fuligula 

 ferina), and the ferruginous duck (Fuligula nyroca). It is true 

 that in these instances the parent species are in structure and 

 habits very nearly allied, and the only difference of importance 

 is, that the summer duck has eight pairs of ribs, the others 

 have nine ; but an extra pair of ribs is no proof of specific 

 distinctness, for in man an extra pair occurs occasionally, and 

 in the anthropoid apes there is sometimes a pair of ribs and 

 one or two vertebras above the typical number, and the ribs 

 themselves are but elongations of processes with which every 

 segment of the vertebral column is furnished. But these facts 

 compel us to ask still more eagerly, what is a species ? Are 

 the three species of duck just named specifically identical, and 

 did the hare and the rabbit originally proceed from the same 

 stock ? 



It will be observed that the most notorious cases of hybri- 

 dization and variation occur in connection with the interference 

 of man with the proceedings of Nature. Wild varieties are 

 plentiful, but the range of variation is more limited. The first 

 object of man, whether he subjects animals to an artificial mode 

 of life for profit or amusement, is to cause them to produce 

 varieties. One way or another he invariably makes attack on 

 the organs of reproduction, or attempts a diversion of their 

 function from its normal course ; and it is worth considering 

 whether he does not unintentionally bring into action circum- 

 stances that will some day bring about an extinction of his 

 varieties, unless their vigour is occasionally replenished by the 

 infusion into it of wild blood. The frequent crossing of the 

 most valued varieties of domestic animals indicates somewhat 

 of a recognition of this fact, that varieties tend to die out. In 

 the case of the animals used in agriculture, the practice of 

 castration must have some effect in diminishing the vigour of 

 races. The males castrated are at once removed for ever from 



* Proceedings of Zoological Society, Feb. 12, 18G1, paper by Edward Crisp, 

 M.D., F.L.S. 



