276 CORVIDvE. 



rests upon its novelty in regard to British authorities* . The 

 case, it must he owned, is one of a rare kind, and, though 

 certainly not singular in ornithology, we have at present to 

 go to India or the heart of North America to find its 

 parallels!. Yet its rarity is no valid objection. If there he 

 any degree of truth in the theories which have of late years 

 been so prominently set forth, such cases must at one time 

 or another have been countless ; but to discuss those theories 

 would here be out of place. All that is now required is 

 to consider, with the utmost fairness, the peculiar characters 

 of each form under every aspect whether of structure, 

 coloration, habits or distribution, and then to test their 

 value in regard to the admitted fact of the frequent inter- 

 breeding of the two forms where they both occur, as well as 

 to the indisputable results of that interbreeding. For this 

 purpose it will be convenient to invert the order generally 

 followed in the present work, and first to describe each form. 

 In the technical sense of the term not an atom of struc- 

 tural difference has been found between the Black and the 

 Grey Crows. Taking in hand a typical specimen of each 

 there is nought to distinguish them but colour. The Grey 

 Crow varies in size as it varies in shade examples from 

 southern countries are smaller, and have their lighter 

 plumage of a clearer tint, than those from the north ; but 

 as regards bulk the Black Crow varies in like manner, and in 

 both the females are less than the males. The whole length 

 of either form is from eighteen and a half to twenty inches ; 

 the wing, from the carpal joint to the tip, is from twelve to 

 fourteen inches ; the first primary is about three inches 

 shorter than the second, which is an inch shorter than the 

 third, and this is a little shorter than the fourth. The tail 



* The notion, however, has long prevailed in the mind or the imagination of 

 some of those best fitted to exercise either. As an example, the excellent 

 remarks on this subject of Mr. Hancock in his ' Birds of Northumberland and 

 Durham ' (pp. 32-36) may especially be cited. 



t Instances more or less similar are found in the interbreeding of certain 

 "species" of Himalayan Pheasants (Oallopliasis the Euplocamus of some 

 authors), of Rollers (Coracias indicus ard C. affinis) in India, and of the North- 

 American Woodpeckers of the genus Colaptes. 



