140 DOMESTIC pigeons: Chap. v. 



classifioation " miglit be followed which woild present fewer 

 difficulties than a " natural classification ;" but then it would 

 iuterrujDt many plain affinities. Extrenie forms can readily 

 be defined ; but intermediate and troublesome forms often 

 destroy our definitions. Forms which may be called " aber- 

 rant " must sometimes be included within groups to which 

 they do not accurately belong. Characters of all kinds must 

 be used ; but as with birds in a state of nature, those afforded 

 by the beak are the best and most readily appreciated. It 

 is not possible to weigh the importance of all the characters 

 which have to be used so as to make the groups and sub-groups 

 of equal value. Lastly, a group may contain only one race, and 

 another and less distinctly defined group may contain several 

 races and sub-races, and in this case it is difficult, as in the 

 classification of natural species, to avoid placing too high a 

 value on the number of forms which a group may contain. 



In my measurements I have never trusted to the eye ; and 

 when speaking of a part being large or small, I always refer 

 to the wild rock -pigeon (Columba livia) as the standard of 

 comparison. The measurements are given in decimals of an 

 inch.^ 



I will now give a brief description of all the principal 

 breeds. The diagram on the following page may aid the 

 reader in learning their names and seeing their affinities. 

 The rook-pigeon, or Columba livia (including under this name 



' As I so often refer to the size of tween the measuremeuts of two wild 

 the C. livia, or rock-pigeon, it may birds, kindly sent me by Dr. Edmond- 

 be coDvenient to give the mean be- stone from the Shetland Islands. 



Inches. 



Length from feathered base of beak to end of tail 14'25 



„ » » to oil-gland 9-5 



„ from tip of beak to end of tail 15-02 



„ of tail-feathers 4'6'2 



„ from tip to tip of wing _ .. 26'75 



„ of folded wing 9'25 



Beak. — Length from tip of beak to feathered base '77 



„ Thickness, measured vertically at distal eud of nostrils .. .. 23 



„ Breadth, measured at same place •16 



Feet. — Length from end of middle toe (without claw) to distal end ofl „.„„ 



tibia / 



„ Length from end of middle toe to enc of hind toe (withoufl .^-oa 



claws) / 



Weight 14| ounces. 



