658 Mr. R. Shelford on t/ie Pttrylosis of the 



slit-like and open downwards; the foot is now zyji;odactyious, 

 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. B). 



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. ven trails have not increased in extent. 

 There have, however, now appeared on the tliroat 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 

 bodv. 



