not any of the characters of the domestic breeds。 Hence the supposed aboriginal stocks must either still exist in the countries where they were originally domesticated； and yet be unknown to ornithologists； and this； considering their size； habits； and remarkable characters； seems very improbable； or they must have become extinct in the wild state。 But birds breeding on precipices； and good fliers； are unlikely to be exterminated； and the common rock…pigeon； which has the same habits with the domestic breeds； has not been exterminated even on several of the smaller British islets； or on the shores of the Mediterranean。 Hence the supposed extermination of so many species having similar habits with the rock…pigeon seems to me a very rash assumption。 Moreover； the several above…named domesticated breeds have been transported to all parts of the world； and； therefore； some of them must have been carried back again into their native country； but not one has ever become wild or feral； though the dovecot…pigeon； which is the rock…pigeon in a very slightly altered state； has become feral in several places。 Again； all recent experience shows that it is most difficult to get any wild animal to breed freely under domestication； yet on the hypothesis of the multiple origin of our pigeons； it must be assumed that at least seven or eight species were so thoroughly domesticated in ancient times by half…civilized man； as to be quite prolific under confinement。
An argument； as it seems to me； of great weight； and applicable in several other cases； is； that the above…specified breeds； though agreeing generally in constitution； habits； voice； colouring； and in most parts of their structure； with the wild rock…pigeon； yet are certainly highly abnormal in other parts of their structure： we may look in vain throughout the whole great family of Columbidae for a beak like that of the English carrier； or that of the short…faced tumbler； or barb； for reversed feathers like those of the jacobin； for a crop like that of the pouter； for tail…feathers like those of the fantail。 Hence it must be assumed not only that half…civilized man succeeded in thoroughly domesticating several species； but that he intentionally or by chance picked out extraordinarily abnormal species； and further； that these very species have since all become extinct or unknown。 So many strange contingencies seem to me improbable in the highest degree。
Some facts in regard to the colouring of pigeons well deserve consideration。 The rock…pigeon is of a slaty…blue； and has a white rump （the Indian sub…species； C。 intermedia of Strickland； having it bluish）； the tail has a terminal dark bar； with the bases of the outer feathers externally edged with white； the wings have two black bars： some semi…domestic breeds and some apparently truly wild breeds have； besides the two black bars； the wings chequered with black。 These several marks do not occur together in any other species of the whole family。 Now； in every one of the domestic breeds； taking thoroughly well…bred birds； all the above marks； even to the white edging of the outer tail…feathers； sometimes concur perfectly developed。 Moreover； when two birds belonging to two distinct breeds are crossed； neither of which is blue or has any of the above…specified marks； the mongrel offspring are very apt suddenly to acquire these characters； for instance； I crossed some uniformly white fantails with some uniformly black barbs； and they produced mottled brown and black birds； these I again crossed together； and one grandchild of the pure white fantail and pure black barb was of as beautiful a blue colour； with the white rump； double black wing…bar； and barred and white…edged tail…feathers； as any wild rock…pigeon！ We can understand these facts； on the well…known principle of reversion to ancestral characters； if all the domestic breeds have descended from the rock…pigeon。 But if we deny this； we must make one of the two following highly improbable suppositions。 Either； firstly； that all the several imagined aboriginal stocks were coloured and marked like the rock…pigeon； although no other existing species is thus coloured and marked； so that in each separate breed there might be a tendency to revert to the very same colours and markings。 Or； secondly； that each breed； even the purest； has within a dozen or； at most； within a score of generations； been crossed by the rock…pigeon： I say within a dozen or twenty generations； for we know of no fact countenancing the belief that the child ever reverts to some one ancestor； removed by a greater number of generations。 In a breed which has been crossed only once with some distinct breed； the tendency to reversion to any character derived from such cross will naturally become less and less； as in each succeeding generation there will be less of the foreign blood； but when there has been no cross with a distinct breed； and there is a tendency in both parents to revert to a character； which has been lost during some former generation； this tendency； for all that we can see to the contrary； may be transmitted undiminished for an indefinite number of generations。 These two distinct cases are often confounded in treatises on inheritance。
Lastly； the hybrids or mongrels from between all the domestic breeds of pigeons are perfectly fertile。 I can state this from my own observations； purposely made on the most distinct breeds。 Now； it is difficult； perhaps impossible； to bring forward one case of the hybrid offspring of two animals clearly distinct being themselves perfectly fertile。 Some authors believe that long…continued domestication eliminates this strong tendency to sterility： from the history of the dog I think there is some probability in this hypothesis； if applied to species closely related together； though it is unsupported by a single experiment。 But to extend the hypothesis so far as to suppose that species； aboriginally as distinct as carriers； tumblers； pouters； and fantails now are； should yield offspring perfectly fertile； inter se； seems to me rash in the extreme。
From these several reasons； namely； the improbability of man having formerly got seven or eight supposed species of pigeons to breed freely under domestication； these supposed species being quite unknown in a wild state； and their becoming nowhere feral； these species having very abnormal characters in certain respects； as compared with all other Columbidae； though so like in most other respects to the rock…pigeon； the blue colour and various marks occasionally appearing in all the breeds； both when kept pure and when crossed； the mongrel offspring being perfectly fertile； from these several reasons； taken together； I can feel no doubt that all our domestic breeds have descended from the Columba livia with its geographical sub…species。
In favour of this view； I may add； firstly； that C。 livia； or the rock…pigeon； has been found capable of domestication in Europe and in India； and that it agrees in habits and in a great number of points of structure with all the domestic breeds。 Secondly； although an English carrier or short…faced tumbler differs immensely in certain characters from the rock…pigeon； yet by comparing the several sub…breeds of these breeds； more especially those brought from distant countries； we can make an almost perfect series between the extremes of structure。 Thirdly； those characters which are mainly distinctive of each breed； for instance the wattle and length of beak of the carrier； the shortness of that of the tumbler； and the number of tail…feathers in the fantail； are in each breed eminently variable； and the explanation of this fact will be obvious when we come to treat of selection。 Fourthly； pigeons have been watched； and tended with the utmost care； and loved by many people。 They have been domesticated for thousands of years in several quarters of the world； the earliest known record of pigeons is in the fifth Aegyptian dynasty； about 3000 B。C。； as was pointed out to me by Professor Lepsius； but Mr Birch informs me that pigeons are given in a bill of fare in the previous dynasty。 In the time of the Romans； as we hear from Pliny； immense prices were given for pigeons； 'nay； they are come to this pass； that they can reckon up their pedigree and race。' Pigeons were much valued by Akber Khan in India； about the year 1600； never less than 20；000 pigeons were taken with the court。 'The monarchs of Iran and Turan sent him some very rare birds；' and； continues the courtly historian； 'His Majesty by crossing the breeds； which method was never practised before； has improved them astonishingly。' About this same period the Dutch were as eager about pigeons as were the old Romans。 The paramount importance of these considerations in explaining the immense amount of variation which pigeons have undergone； will be obvious when we treat of Selection。 We shall then； also； see how it is that the breeds so often have a somewhat monstrous character。 It is also a most favourable circumstance for the production of distinct breeds； that male and female pigeons can be easily mated for life； and thus different breeds can be kept together in the same aviary。
I have discussed the probable origin of domestic pigeons at some； yet quite insufficient； length； because when I first kept pigeons and watched the several kinds； knowing well how true they bred； I felt fully as much difficulty in believing that they could ever have descended from a common parent； as any naturalist could in coming to a similar conclusion in regard to the many species of finches； or other large groups of birds； in nature。 One circumstance has struck me much； namely； that all the breeders of the various domestic animals and the cultivators of plants； with whom I have ever conversed； or whose treatises I have read； are firmly convinced that the several breeds to which each has attended； are descended from so many aboriginally distinct species。 Ask； as I have asked； a celebrated raiser of Hereford cattle； whether his cattle might not have descended from long horns； and he will laugh you to scorn。 I have never met a pigeon； or poultry； or duck； or rabbit fancier； who was not fully convinced that each main breed was descended from a distinct species。 Van Mons； in his tre