Pterylograpliy of the Hoatzin. 358 



callosity, instead of dividing at some distance in front of 

 this point. 



The mode and rate of development of the nestling-plumage 

 reveals some points of considerable interest. 



In stage 1 (PI, X. figs. 1-3) the body is but scantily 

 clothed by the neossoptiles* ; between these, minute specks, 

 arranged more or less definitely in rows, can be seen ; these 

 are the tips of developing plumulse or down-feathers, con- 

 cerning vrhich we shall have more to say later. 



Pt. alaris (PI. XL fig. 2). — Here it will be noticed that 

 the remiges are just beginning to make their appearance, 

 bearing out the ueossoptiles on their tips. The proximal 

 primaries are furthest developed; the proximal cubitals are 

 indicated by neossoptiles. 



T. majores. — These are, as yet, only represented by neos- 

 soptiles above their respective remiges. The remaining tec- 

 trices are represented by the tips of the neossoptiles breaking 

 through the skin. 



Stage 2. The plamulse have increased in size so as to 

 appear like little brush-like tufts ; but on the head and 

 back part of neck they remain much as in stage 1 . 



Pt. alaris : — 



Primaries. — These have now pushed their way out a 

 considerable distance beyond the wing, the individual remiges 

 preserving the same relative lengths as in stage 1 ; remex 10, 

 however, must be excepted, inasmuch as nothing but the 

 neossoptiles can be seen. 



Cubitals. — Preserve the same relative length as in stage 1 ; 

 the proximal remiges are as yet only indicated by neos- 

 soptiles. 



Tectrices : — - 



T. majores. — The definitive feathers on the dorsal surface 

 of this series are now making their appearance. The re- 

 mainder of the coverts are as yet only represented by neos- 

 soptiles. The under surface of the wing appears as though 



* For the origin and meaning of this term see ' Dictionary of Birds,' 

 Newton, Article " Feathers," p. 243. 



SER. VII. VOL. I. 2 C 



