Jeffries.] 214 [February 7, 



figure 38 of his article, are not remiges, but coverts, the pockets 

 of which, on account of their inferior size, are simply born out 

 upon the pockets of the remiges. Even in Studer's figure, this 

 is shown by the covert of the fourth primary, which is clearly 

 in a separate pocket upon that of the primary. 



Turning now to the structure of the papilla and pocket, it is 

 clearly shown by longitudinal sections that the layers of the epi- 

 derm are continued from the walls of the pocket on to the papilla. 

 At this period the structure of the epiderm is very simple and 

 consists of the mucous layer and a thin layer of roundish transi- 

 tional cells outside. The horn cells have all been shed with the 

 old feather. Very shortly the transitional cells begin to form 

 in large numbers and cause the epiderm of the papilla to excel 

 greatly in thickness that of the pocket; soon after the tip of the 

 pulp has appeared above the surface, or even before, several 

 changes occur (fig. 11). The outer layer of cells (a) covering 

 the feather-sack becomes very much flattened, polygonal, and 

 forms a thin sheath (fig. 10) which resembles remarkably the 

 epitrichial layer of the embryo. In position and structure it is 

 very much the same, and cannot be told from the epitrichial cells 

 covering the primaries of young passerine birds. Beneath this 

 is a layer of flat horn cells (fig. 11 b) formed from the outer 

 transitional cells. The inner transitional cells together with those 

 of the mucous layer still retain their primitive character. Yet 

 changes have occurred in their arrangments ; they no longer form 

 a simple sheath around the pulp of cutis vera, but two thicken- 

 ings exist each one destined to form a barb. These are rapidly 

 followed by others added on at the sides until the entire surface 

 is occupied. The first two formed shortly join and start the 

 two halves of the shaft and are later joined by those on the 

 sides. So all but the two first folds do not run parallel to the 

 long axis of the papilla, but slant towards the first two, or 

 primary, folds ; the folds on the left side joining the left pri- 

 mary fold, and those on the right the right primary fold. As 

 yet the shaft is a solid rod, the composite nature of which can be 

 traced in many adult feathers 



After the feather is somewhat grown the composite structure 

 of the two sides of the shaft is lost and a fold is seen grow- 

 ing from each side into the [ ulp. These fclds growing round 



