GENERAL INTEOBUCTION. XXVll 



white, and the wings in front of the bars of a uniform 

 light blue colour. In India the croup is generally blue, 

 while the wing coverts are chequered with black. In 

 Madeira, through abundant chequering the front part of 

 the wings often looks almost black. In one of my young 

 birds the croup and wings agree with the Shetland rock- 

 pigeon ; in the other the croup, except near the root of 

 the tail, is blue, and the wing coverts are chequered. 

 They thus may be said to illustrate the whole range of 

 variation in the colour of the croup and wings in the 

 wild rock-pigeon of Europe and Asia. The bird with 

 the white croup has several white feathers about the 

 head, and it thus departs from a typical wild bird ; but 

 the one with a blue croup is in its coloration the image 

 of a chequered rock-pigeon. 



In the bird with chequered wings we have complete 

 reversion, not to the blue rock of Europe so much as to 

 the blue rock of India. The explanation of this may be 

 that the ancestors of both the fautail and the owl were 

 Indian, or at least Eastern birds. If this is so the 

 reversion in the case of the darkest bird is all the more 

 complete and remarkable. 



Having referred to the reversion in colour, the question 

 remains, is there reversion also in form ? Weismann, it 

 will be remembered, took for granted that Darwin^s 

 fantail-barb-spot cross was " a mere case of reversion as 

 regards the coloration of the plumage,^^ and pointed out 

 that " reversion to the blue colour is not necessarily 

 accompanied by a reversion to all the other characters of 

 the ancestral form." In the case of my most typical 

 bird there is, as far as an external examination can show, 

 practically complete reversion. In its measurements it is 

 relatively almost identical with a typical Shetland blue 

 rock. I say relatively because, having only reached 

 maturity, it is not yet full-grown. In its extreme length 

 it is 2 per cent, shorter than a full-grown Shetland bird, 

 and this amount of difference may be said to obtain for 

 the legs, beak, toes, &c. 



In its attitude and movements it resembles the wild 



