HIEUNDO RUSTICA. 87 



Length of wing no doubt adds to the power of flight, though an 

 additional pair would not. It is possible for a bird to have four wings. 

 Mr. St. George Mivart says ('Contemporary Review/ Nov. 1875, p. 949), 

 in his article on likenesses, or Philosophical Anatomy, speaking of teratology 

 or the science of monstrous births : " The feet of Pigeons or Fowls are 

 abnormally feathered, or, as it is termed, furnished with 'boots/ These 

 extra feathers are developed along the very parts of the feet which correspond 

 to (i. e. are serially homologous with) those parts of the bird's hand which 

 bear the wing-feathers ; so that these ' boots ' are plainly a serial repetition 

 of the true wing-feathers. These foot-feathers have, indeed, been sometimes 

 known to exceed the wing-feathers in length. Moreover they resemble the 

 true wing-feathers in structure, and are quite unlike the down which 

 naturally clothes the legs of such birds as Grouse and Owls. But there is a 

 more striking correspondence still ; for in Pigeons which are thus ' booted ' 

 the two outer digits (toes) become more or less connected by skin, as is also 

 the case with the corresponding digits of the Pigeon's hand." 



But though four wings are not necessary, new ones are better than old 

 ones ; and after moulting, stronger flight is acquired, very much as a ship 

 sails faster after having its bottom cleaned. Accordingly, Messrs. Francis 

 Henry Salvin and William Brodrick relate Q Falconry in the British Isles,' 

 2nd edition, p. 87) that Mr. Clough Newcome's Merlins, about 1850, caught 

 Larks, if their bells were taken off^, constantly ; but " after September, when 

 the old Larks were fully moulted, they proved more than a match for the 

 Hawks." 



We should expect that birds must migrate more than other members of 

 the animal kingdom, because food is admitted to be one cause of migration, 

 and they require to feed oftenest of any (serpents, which only eat after long 

 intervals, being the converse), and food must be sought. 



Now, though I consider that when a bird is started on its voyage it is 

 carried by wind, or, rather, guided by it (which I argue to be the case from 



N 2 



