prove of interest to state briefly a few generalizations regarding the 

 comparative development of the young in diiferent families of 

 birds. 



Among North American AUrices the young of most species are 

 born with thin patches of delicate, soft down, restricted mainly to 

 the feather-tracts. Beneath this fluffy down the feathers are 

 already forming; these soon appear, bearing at their summits the 

 little tufts of down that formed the down-patches. Meanwhile the 

 remiges and rectrices have started, and, growing with marvellous 

 rapidity, the bird is soon able to take wing. The contour-feathers 

 have now also nearly reached their full growth, and differ in both 

 structure and color from the later stages of plumage, these feathers 

 being softer and of a more open texture than those that succeed 

 them. This is the stage of plumage technically characterized 

 throughout the following paper as the first plumage. Though eva- 

 nescent, it is usually worn for several weeks after the bird has left the 

 nest. It is theil moulted, and the regular autumnal plumage suc- 

 ceeds. 



The remiges and rectrices are, however, nearly always retained 

 until the next regular moult, exceptions to this rule being afforded 

 by the families Tetraonidce and Picidce and the genus Philohela, 

 and probably by a few other groups, in which the remiges and rec- 

 trices are. moulted with the rest of the first plumage. 



The early tegumentary development of most Prcecoces (birds 

 whose young run about at birth) is quite different : they are 

 densely clothed with down until of large size, when, coincident with 

 the sprouting and gi-owth of the remiges and rectrices, the feathers 

 of the full autumnal plumage appear. In short, the first plumage 

 of Altricial birds seems to be omitted or perhaps replaced in the 

 Prmcoces by their more complete and longer worn, downy plumage. 

 A few conspicuous exceptions occur among both groups. Thus, 

 many Raptores differ from the AUrices in being densely clothed with 

 down from birth until of large size, when the autumnal plumage is 

 immediately assumed; while among Prcecoces the youngof the Tetrao- 

 nidw, of Philohela minor, and of some of the Rallidce (well illus- ' 

 trated by a good suite of Rallus virginianus), pass in succession 

 through two well-defined primal stages, — the downy one character- 

 izing their own group and the first plumage of Altfices. In the 

 AnatidcB, and probably some other Natatores, the remiges and rec- 

 trices are not developed until the young bird is almost fully grown 



