COLOUEING OF HYBRIDS. 357 



which was recently described, the offspring of a cross between the 

 brown bear and the Polar bear, is described as follows.* ' The 

 change of colour undergone by the hybrid young was very in- 

 teresting. All four came into the world quite white, but pre- 

 sently assumed a silvery grey or bluish hue, and at the age of 

 three months were of a dark -brown colour, shot, as it were, with 

 a blue gleam. They at no time showed any trace of the white 

 necklace which is characteristic of the young of the brown bear. 

 The two that are six months old are at present for the most 

 part greyish-brown, but not uniform in colour ; all about the 

 throat they are conspicuously lighter, almost white. The two 

 that are eighteen months old are much lighter altogether ; the 

 backs and sides are a light bay brown ; a dark median band in 

 one of them is tolerably broad and extends all down the back ; 

 in the other it is only faintly indicated in the fore-part; the top 

 of the head is light brown, the under part and the rump 

 whitish, all four extremities a rather dark brown.' It is easily 

 seen from this description that in this case changes in the 

 colouring have been produced in the hybrids which exhibit a 

 very considerable deviation from that of the parents. 



At the same time this last-mentioned instance is particularly 

 adapted to bring into prominence another phenomenon which is 

 at least as conspicuous in the hybridisation of animals as of 

 plants, namely the mixture in the hybrid young of the colouring 

 of both parents, particularly in the hybrids of insects and birds. 

 In these a very distinct combination of part of the colouring of 

 the female with differences taken from the male is regularly re- 

 produced, as the mixture of colours in the hybrid (or mule) of the 

 canary-bird and goldfinch ; in the hybrids above mentioned, 

 between the poplar and wUlow moth, the peculiar marks on the 

 hind wings of the former may be plainly seen overlying the eyes 

 of the latter. But the extent of this mixture is extremely dif- 

 ferent in the individual progeny, as has been evident in the 

 minute description of the hybrid bears ; sometimes the colours 

 of the female predominate, sometimes those of the male, and this 

 may occur in different young of the same brood. Thus it is evi- 

 dent that hybridisation does not result merely in an aggregation 

 * In a German psriodical, 'The Zoological Garden.' 



