I50 THE INFANCY OF ANIMALS 



food of the comparative anatomist. Unusually favourable 

 circumstances have provided me with exceptional oppor- 

 tunities for gratifying my appetite in this direction : 

 as witness the facts already set down in regard to the 

 coloration both of downy nestlings, and of their later, 

 " juvenile " plumages. 



I propose now to set down a few facts which have come 

 my way in the matter of these down plumages apart from 

 the coloration. They do not, by any means, represent 

 the sum of our knowledge of these things, and it is to be 

 hoped that some reader of these lines may be tempted to 

 take up the further development of the problems raised. 



In the first place, be it noted, there are two quite dis- 

 tinct kinds of nestling down. One of these is developed 

 from the same germs as will later give rise to the " con- 

 tour " feathers — that is to say to the outer covering of 

 the adult bird — hence I have called such down feathers 

 " pre-pennae." The other precedes the down feathers 

 which form a sort of " under-fur " in so many birds, e.g. 

 ducks and swans, and hence are called " pre-plumulae." 

 Where no down-feathers are developed in the adult no 

 pre-plumulse occur in the nestling, as for example in the 

 owls. Now the importance of these distinctions does not 

 become apparent untU we begin to compare one nestling 

 with another, as for example young owls with young 

 hawks. 



Those at any rate who are not practised ornithologists 

 would find it no easy matter to distinguish, say, a young 

 Barn Owl from a young kestrel, for both are covered 

 alike in a long white woolly garment of down. But a 

 careful examination of this garment would show the 

 difference at once ; for in the owl only pre-pennae would 

 be found, while in the hawk the downy covering would 



