134 DOMESTIC PIGEONS. Chap. V. 



often destroy our definitions. Forms which may be called 

 "aberrant" 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 characters which are common to a large number of forms. 



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 livid) as the standard of com- 

 parison. The measurements are given in decimals of an ineh. 5 



I will now give a brief description of all the principal breeds. 

 The following diagram may aid the reader in learning their 

 names and seeing their affinities. The rock-pigeon, or Columba 

 livia (including under this name two or three closely-allied 

 sub-species or geographical races, hereafter to be described), 

 may be confidently viewed, as we shall see in the next chapter, 

 as the common parent-form. The names in italics on the right- 

 hand side of the table show us the most distinct breeds, or those 

 which have undergone the greatest amount of modification. The 

 lengths of the dotted lines rudely represent the degree of dis- 

 tinctness of each breed from the parent-stock, and the names 



5 As I so often refer to the size of measurements of two wild birds, kindly 

 the G. livia, or rock-pigeon, it may be sent me by Dr. Edmondstone from the 

 convenient to give the mean between 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 10 v f 



„ of tail-feathers *' 62 



„ from tip to tip of wing 2 » 15 



„ of folded wing 9 "^ 



Beak;. Length from tip of beak to feathered base 



Thickness, measured vertically at further end of nostrils 



Breadth, measured at same place •• 



Feet.— Length from end of middle toe (without claw) to distal end of tibia 2-77 



Length from end of middle toe to end of hind toe (without claws) 2-02 

 Weight 141 ounces. 



