168 



DOMESTIC PIGEONS. 



Chap. V, 



parts vary ; but which of two correlated variations ought to he 

 looked at as the cause and which as the effect, or whether both 

 result from some common cause, we can seldom or never tell. 

 The point of interest for us is that, when fanciers, by the con- 

 tinued selection of slight variations, have largely modified one 

 part, they often unintentionally produce other modifications. 

 For instance, the beak is readily acted on by selection, and, 

 with its increased or diminished length, the tongue increases or 

 diminishes, but not in due proportion ; for, in a barb and short- 

 faced tumbler, both of which have very short beaks, the tongue, 

 taking the rock-pigeon as the standard of comparison, was pro- 

 portionally not shortened enough, whilst in two carriers and 

 in a runt the tongue, proportionally with the beak, was not 

 lengthened enough. Thus, in a first-rate English carrier, in 

 which the beak from the tip to the feathered base was exactly 

 thrice as long as in a first-rate short-faced tumbler, the tongue 

 was only a little more than twice as long. But the tongue varies 

 in length independently of the beak : thus, in a carrier with a 

 beak 1-2 inch in length, the tongue was -67 in length: whilst 

 in a runt which equalled the carrier in length of body and in 

 stretch of wings from tip to tip, the beak was -92 whilst the 

 tongue was *73 of an inch in length, so that the tongue was 

 actually longer than in the carrier with its long beak. The 

 tongue of the runt was also very broad at the root. Of two 

 runts, one had its beak longer by -23 of an inch, whilst its tongue 

 was shorter by *14 than in the other. 



With the increased or diminished length of the beak the length 

 of the slit forming the external orifice of the nostrils varies, but 

 not in due proportion, for, taking the rock-pigeon as the standard, 

 the orifice in a short-faced tumbler was not shortened in due 

 proportion with its very short beak. On the other hand (and 

 this could not have been anticipated), the orifice in three 

 English carriers, in the Bagadotten carrier, and in a runt 

 ('pigeon cygne), was longer by above the tenth of an inch than 

 would follow from the length of the beak proportionally with 

 that of the rock-pigeon. In one carrier the orifice of the nostrils 

 was thrice as long as in the rock-pigeon, though in body and 

 length of beak this bird was not nearly double the size of the 



