78 PERPETUATION OF LIVING BEINGS 



is to say, a notification of the various points in wnich 

 their organization differs. In the first place, the back 

 of the skull may differ a good deal, and the development 

 of the bones of the face may vary a great deal ; the back 



k-s a good deal ; the shape of the lower jaw varies ; 

 tongue varies very greatly, not only in correlation to 

 the length and size of the beak, but it seems also to have 

 a kind of independent variation of its own. Then the 

 amount of naked skin round the eyes, and at the base of 

 the beak, may vary enormously ; so may the length of the 



lids, the shape of the nostrils, and the length of the 

 neck. I have already noticed the habit of blowing out 

 the gullet, so remarkable in the Pouter, and comparatively 

 so in the others. There are great differences, too, in the 

 size of the female and the male, the shape of the body, the 

 number and width of the processes of the ribs, the develop- 

 ment of the ribs, and the size, shape, and development of 

 the breastbone. We may notice, too, and I mention the 

 fact because it has been disputed by what is assumed to 

 be high authority, the variation in number of the sacral 

 vertebrae. The number of these varies from eleven to 

 fourteen, and that without any diminution in the number 

 of the vertebrae of the back or of the tail. Then the number 

 and position of the tail-feathers may vary enormously, 

 and so may the number of the primary and secondary 

 feathers of the wings. Again, the length of the feet and 

 of the beak, although they have no relation to each other, 

 yet appear to go together, that is, you have a long beak 

 wherever you have long feet. There are differences also 

 in the periods of the acquirement of the perfect plumage, 

 the size and shape of the eggs, the nature of flight, and 

 the PO\VCTS of flight, so-called " homing " birds having 

 enormous flying powers ; * while, on the other hand, the 

 lillle Tumbler is so called because of its extraordinary 

 faculty of turning head over heels in the air, instead of 

 pursuing a distinct course. And, lastly, the dispositions 

 and voices of the birds may vary. Thus the case of the 

 pigeons shows you that there is hardly a single particular, 

 whether of instinct, or habit, or bony structure, or of 

 plumage, of either the internal economy or the external 



* The " Carrier," I learn from Mr. Tegctmeier, does not carry ; a 

 high-bred bird of this breed beinjj but a poor llicr. The birds which 

 fly long distances, and come home, " homing " birds, and are 

 consequently used as carriers, are not " carriers " in the fancy sense. 



