513 



SEQUENCE IN MOULTS AND PLUMAGES, WITH 

 AN EXPLANATION OP PLUMAGE-CYCLES. 



By Jonathan Dwight, Jr., M.D. 



Sequence is a principle so basic in the workings of Nature 

 that its importance is apt to be overlooked in explaining" that 

 which seems to be obscure and complicated, and certainly 

 in plumages and moults, unless , their natural sequence is 

 thoroughly understood, there is much that seems hopelessly 

 obscure. Sequence is basic in the growth of a feather where 

 the barbules are differentiated before the barbs, and the 

 barbs in their turn before the shaft ; so, too, the apex is 

 formed before the proximal quill portion has even taken 

 shape. This much the histologist with the microscope and 

 methods of a modern laboratory vouches for, while the 

 ornithologist concerns himself more particularly with the 

 successive generations of feathers or plumages that clothe 

 the bird in regular sequence. The first generation is known 

 as neossop tiles, which are down-like in character; the second as 

 mesoptiles, which lack the characters of fully adult feathers ; 

 and the third and later generations are known as teleoptiles, 

 or mature feathers of various types. 



It is not, however, to the feathers themselves that I wish 

 to draw especial attention, but to the plumages or aggrega- 

 tions of feathers which grow and are cast off at definite 

 periods in a bird's life, namely, at times of moult. The 

 sequence of plumages and moults is as regular as is the order 

 of cell-proliferation in the feather-germ, but the order of the 

 plumages is not the same for every species. A complete 

 moult, which rarely occurs more than once in a twelvemonth, 

 results in a simple plumage, while partial moults result in 

 compound plumages, made up of the feathers of several 

 generations. Each species has a definite series of plumages 

 that constitute a cycle to which the individuals of that 

 species conform, the cycles differing in different species. 

 Neither moults nor plumages have been thoroughly under- 

 stood, and I may well be pardoned my repetition, before an 



