{442} In a corresponding passage in the _Origin_, Ed. i. p. 423, vi. p. 579, the author makes use of his knowledge of pigeons. The pseudo-genera among dogs are discussed in _Var. under Dom._, Ed. ii. vol. I. p. 38. {443} _Origin_, Ed. i. pp. 419, 427, vi. pp. 575, 582. {444} _Origin_, Ed. i. pp. 423, 427, vi. pp. 579, 583. {445} _Origin_, Ed. i. p. 423, vi. p. 579. I think it cannot be doubted that the main cause of all the varieties which have descended from the aboriginal dog or dogs, or from the aboriginal wild cabbage, not being equally like or unlike--but on the contrary, obviously falling into groups and sub-groups--must in chief part be attributed to different degrees of true relationship; for instance, that the different kinds of blood-hound have descended from one stock, whilst the harriers have descended from another stock, and that both these have descended from a different stock from that which has been the parent of the several kinds of greyhound. We often hear of a florist having some choice variety and breeding from it a whole group of sub-varieties more or less characterised by the peculiarities of the parent. The case of the peach and nectarine, each with their many varieties, might have been introduced. No doubt the relationship of our different domestic breeds has been obscured in an extreme degree by their crossing; and likewise from the slight difference between many breeds it has probably often happened that a "sport" from one breed has less closely resembled its parent breed than some other breed, and has therefore been classed with the latter. Moreover the effects of a similar climate{446} may in some cases have more than counterbalanced the similarity, consequent on a common descent, though I should think the similarity of the breeds of cattle of India or sheep of Siberia was far more probably due to the community of their descent than to the effects of climate on animals descended from different stocks. {446} A general statement of the influence of conditions on variation occurs in the _Origin_, Ed. i. pp. 131-3, vi. pp. 164-5.