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Show 40 DR. J. MURIE ON IRREGULARITY [Jan. 13, ledge, are so stunted when full-grown. Thus it follows that either lessened dimension is a result of hybridity, or the two specimens a distinct species per se. In a conversation with my colleague Mr. Bartlett concerning this same question of hybridism and the size of the offspring, I received such information, based on his long experience among animals, that I think it worthy of incorporation in the present paper. From it some hints applicable to fish may be derived, or at least borne in mind, in discussing piscine forms. His proposition is, " That among all hybrids of vertebrated animals there is a marked increase of size." In no instance coming under his observation has the offspring been smaller than both its parents. In other words, it is always larger than the lesser-sized parent; that is, supposing inequality of dimensions between the parents to exist. Among Mammals the following examples may be cited:- 1, Hybrids between Horse and Ass; 2, the Common Zebra and Common Ass; 3, Burchell's Zebra and the Common Ass; 4, the Wild Ass (Equus onager) and the Zebra; 5, the Bactrian and Common Camel; 6, the Alpaca and Llama; 7, the Yak and Zebu ; 8, the Barbary and Red Deer; 9, the Rhesus and Bonnet Monkey; 10, the Black-fronted and Yellow-cheeked Lemurs (L. nigrifrons and L. xanthomystax) ; 11, Bennett's and the Rufous Kangaroo (Halmaturus bennettii and H. ruficollis). Among Birds:- 12. Hybrids between the Common Canary and the following, viz. the Greenfinch, the Goldfinch, the Linnet, and the Siskin. 13. Among the Galinaceous Birds, hybrids between the Common Pheasant and the Silver Pheasant, the Gold Pheasant and the Bar-tailed Pheasant; also hybrids between the Common Pheasant and the Common Fowl, the Guinea-fowl and the Black Grouse. 14. Hybrids between the Black Cock and the Wood-grouse; in this case the offspring is termed Tetrao medius because of the constancy of this very peculiarity as regards size. 15. Of Struthious Birds one cross only has come under Mr. Bartlett's notice, namely a hybrid between the Great-billed and the Common Rhea. Curiously enough, this offspring was larger than either of the parents. 16. Among Waterfowl a very large number might be adduced as evidence ; but the subjoined may suffice :-Hybrids between the Common Goose and the Chinese species, the Canada, the White-fronted, and the Barnacle Goose (indeed cross breeds amongst va-lious sorts of Domestic and Wild Geese have many times been observed by him) ; hybrids between the Common Wild Duck, the Wigeon, the Pintail, the Teal, and the Muscovy Duck. These and other instances of Waterfowl have frequently come under his notice ; and in all cases the afore-mentioned law applies. As respects fishes, authentic observations upon hybrid progeny are meagre ; but I may quote some experiments made at Stormontfield. In November and December 1857 provision was made forhatchin°- 1 ***> |