164 



BRITISH BIRDS. 



I have shown elsewhere (in my Beport on the A7iatomy 

 of the Fenguins, published by the British Museum) that 

 nestlings originally developed two distinct, successive, nest- 

 ling-down plumages ; two distinct generations of pre-pennce. 

 In no case does the first generation retain its original 

 character, and in the majority of instances it appears to 

 be absent altogether, only the second generation being 

 preserved, while in a great number of species even this 

 has been suppressed, as for instance in the Crows and in 

 the Sparrows. 



Fig. 4. — A Mesoptyle Down Feather of a nestling Tawny Owl. 

 Note the weil-develoiDed shaft and lateral '' barbs." 



Among British birds these two distinct generations of 

 down-plumage, preceding the advent of the typical feathers. 



