ON THE CHANGE OF COLOUR IN BIRDS. 85 
“border-casting.”* This has been observed and explained in 
various ways. 
With the assistance of some sketches I have made, I will now 
endeavour to answer the chief question—Whether the colouring 
matter in certain feathers is found there ab initio, or is evolved 
there during the spring or pairing season ? 
According to the phraseology employed by Nitzsch, a feather 
consists of the stem (scapus), the branches (rami), and the 
plumules (radi). From the stem, branches proceed on either 
side, and from these again plumules; but these last named are 
not always on the sides, but sometimes on the top of the branches. 
The small ciliz and hamuli which are fastened on the radii, and 
whose province it is to hold these together, are here passed over, 
as they have nothing to do with the change of colour. t 
If we examine the feathers of different birds with the “ winter 
border” under the microscope, we find that behind the white, 
dark, or colourless outermost points, the colouring matter in 
some is found in the radii, in others in the rami. Thus there 
are two forms which may be called, according to their subsequent 
changes, “ plain point casting” and “ point and radii casting.” 
1. Point casting takes place in those birds which have the 
colouring matter usually in the radii. The colourless or coloured 
points commence, after the autumn moult, to fall off by degrees ; 
but this casting off is not completed until towards the spring, or 
much later, and then the hitherto concealed colour shows itself 
in its full beauty. . 
PuateE I., fig. 1 shows the upper portion of a black throat- 
feather, in autumn, with its white points,-of a male Redstart, 
Ruticilla phenicurus: fig. 2, a similar feather in the spring. The 
points are cast even with the coloured portion. To this group 
belong Fringilla montifringilla, domestica, montana, celebs, chloris, 
spinus, Emberize, Alaude, Sturnus, Turdus (T’. torquatus), Parus, 
Sazxicola enanthe, Sylvia tithys, suecica (the reddish brown and 
black feathers on the breast), many birds that have a partial 
* That other causes than this may effect a change in colour in some few Swedish 
birds, as Coracias garrula, Lanius collurio, and others might be a subject for 
enquiry on some future occasion. 
+ See Prof. Sundevall’s work on the wings of birds (Vet, Ak, Hand]. 1843). 
