658 
Mr. R, Shelford on the Pterylosis of the 
slit-like and open downwards; the foot is now zygodactylous, 
but the long spur-like claw of the hallux is not yet developed, 
the claws of all the toes being approximately equal. The 
papilla of the oil-gland is markedly elongate. 
Stage 2 (fig. 1, p. 655). —There are no very striking differ, 
ences between the young nestling of this stage and the embryo 
just described, save in the matter of size. None of the actual 
definitive feathers have even yet appeared, but though the 
longest trichoptiles have increased in length from 30 mm. to 
40 mm., there is no increase in their numbers, with the 
result that the body of the nestling appears less densely 
clothed than formerly. Furthermore, owing to the rubbing 
of the nestling against the sides of the nest, its fellows and 
other external objects, the trichoptiles stand out at all sorts 
of angles to the body, giving it a very dishevelled appearance 
(Plate XIII. R). 
To my description of the pterylse and apteria of the 
embryo I have little to add. Some minute tips have appeared 
along the lower border of the eye, but otherwise the pt. 
capitis is unchanged, and the same may be said of the 
pt. spinalis, pt. humeralis *, pt. femoralis, and pt. cruralis. 
The pt. colli lateralis is as distinct as before, whilst the 
trichoptiles of the pt. ventralis have not increased in extent. 
There have, however, now appeared on the throat and on 
each side of the upper part of the breast numerous papillae 
arranged in distinct chevrons; protruding from some of 
these papillae may be seen the minute tips of the future 
feathers. 
Pt. alaris (fig. 3, p. 659).—As the fore-limb has now con¬ 
siderably increased in size, it is now possible to make 
out quite clearly the different members of this tract 
and their relations one to the other; and as the tri¬ 
choptiles are no more numerous than in Stage 1, this 
description will apply equally to this stage and to that. 
* The gap between the pt. humeralis and pt. femoralis is somewhat 
greater than in Stage 1, but this is owing to increase in the size of the 
body. 
