HEREDITARY TRANSMISSION AND VARIATION. 105 



it has been disputed by what is assumed to be high 

 authority, — the variation in number of the sacral ver- 

 tebrae. The number of these varies from eleven to four- 

 teeuj 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 

 enormovisly, 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 powers of flight, — so-called " homing " birds 

 having enormous flying powers ;* while, on the other 

 hand, the little 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 shape, in whicli 

 some variation or change may not take place, which, 

 by selective breeding, may become perpetuated, and 

 form the foundation of, and give rise to, a new race. 



* The " Carrier," I learn from Mr. Tegetmeier, does not earn/ ; a 

 Mgh-bred bird of this breed being but a poor flier. The birds which 

 fly long distances, and come home, — " homing " birds, — and are con- 

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



