CiiAr. VIII 



EFFECTS OF USE AND DISUSE. 



21):) 



elongated. In the sternum, I'urcnlnm, coracoids, and sca])ulie, tlit 

 difiereuccs are so slight and so variable as not to be worth notice, 

 except that in two skeletons of the Penguin duck the teiminal 

 portion of the scapula was much attenuated. 



In the bones of the leg and wing no modification in shape could 

 be observed. But in the Penguin and Hook-billed ducks, the 

 terminal jihalanges of the wing are a little shortened. In the 

 former, the femur, and metatarsus (but not the tibia) are con- 

 siderably lengthened, relatively to tlie same bones in the wild duck, 

 and to tlie wing-bones in both birds. This elongation of the leg- 

 bones could be seen whilst the liird was alive, and is no doubt 

 connected with its peculiar upriglit manner of walking. In a 

 large Aylesbury duck, on the other hand, the tibia wr.s the only 

 bone of the leg which relatively to the other bones was slightly 

 lengthened. 



Un fhf effrcfs <•/ the increased and decreased Use of the LIndis. — In 

 all the breeds the bones of the wing (measured separately after 

 having been cleaned) relatively to those of the leg have Ijccome 

 slightly shortened, in comparison with the same bones in the wild 

 duck, as may be seen in the following table ;— 



Name of Hre 'li. 



Wild ninllard 

 AvI(_-.sl)Urv .. 

 Tiirtcil (Uutch) 

 Penguin 

 Call .. .. 



Will] durk (another s-peci- 



meu) 



Common douiestic duck . . 



Length of same I Length of all the 

 Bones. lioiies oi Wing. 



ini-hes 



C. • S5 

 8- 1.5 



hiclie-. 



10-07 

 II -20 



Kin : 117 

 IdO : i:;8 



In the foregoing table we see, by comparison with the wild duck, 

 that the reduction in the length of the bones of the wing, re- 

 latively to those of the legs, though slight, is universal. The 

 reduction is least in the Call duck, which has the power and the 

 habit of frequently flying. 



In weight there is a greater relative difference between the bones^ 

 of the leg and v.ing, as may be seen in the following table : — 



