ROOK. 107 



conclusive on this point ; but the possibility of an entire 

 species being endowed with an instinct destructive of a 

 usual portion of its organisation, was probably never con- 

 templated by these observers ; it is not surprising, there- 

 fore, that the inference, deduced from a partial view of the 

 subject, should be erroneous." 



1 have figured at page 94, a representation of an elonga- 

 tion of the under mandible in a Rook. I have now in my 

 collection an example of a Rook in which the upper man- 

 dible is still more elongated and curved downwards, so as 

 to render it most improbable that this bird could have 

 obtained any part of its food by digging; yet in this 

 specimen the skin around the base of the under mandible 

 is quite destitute of feathers. This would indicate that 

 the want of feathers on the throat, which in this instance 

 could not have been induced by abrasion when digging, 

 was a specific peculiarity ; but it is also possible that this 

 nakedness might have been produced before the alteration 

 in the form of the beak had taken place, and the bulbs 

 from which the feathers arise, having been once injured, 

 might afterwards remain unproductive. 



