Rudimentary Hallux of the Kittiwake. 443 



developmeut, from tlie great Kittiwake nurseries at the 

 Shiant Islands. These embryonic specimens^ and an almost 

 full-fledged nestling and a mature bird, both in the flesh, 

 kindly obtained for me by Mr. F. P. Johnson, together with 

 a series of skins from the collections of Messrs. Feilden and 

 Harvie-Browa, Mr. William Evans, and the Museum of 

 Science and Art, Edinburgh, form the material upon which 

 the following notes are based. From this material I selected 

 certain specimens exhibiting as many stages of development 

 as possible, and from these a series of preparations were 

 made for microscopical examination. 



An examination of the skins of the immature and adult 

 specimens has resulted in my finding that in the great 

 majority the hallux is present in a rudimentary state, usually 

 from '10 to *13 inch in length; and in the minority of these 

 specimens as a mere tubercle. I have only, however, noted 

 the presence of a nail on the hallux in a single adult bird — 

 an interesting specimen from Spitzbergen, obtained at Hecla 

 Bay on the 14th of July, 1827, one of a small series of birds 

 in the Edinburgh Museum obtained by Captain Parry in his 

 celebrated attempt to reach the North Pole. In this bird 

 the nail is very minute, is situated about the centre of the 

 dorsal surface, and does not reach nearly to the end of the 

 digit. Two immature specimens also had nails. One of 

 these, six months old, had the nail extending almost to the 

 apex of the hallux in the form of a thin narrow plate or 

 scale. 



The following notes refer to the microscopical examination 

 of the embi'vos of various ages, and of the nestling and adult 

 already alluded to as received in the flesh. 



In three early embryos of twelve days and under, of which 

 both transverse and longitudinal sections of the foot were 

 prepared, there was not a trace of a nail to be found on cmy 

 of the toes, or even a thickening of the epidermis in the future 

 nail-area. The epithelium presented an unbroken surface, 

 owing to the absence of scutes. 



An embryo estimated to be eighteen days old had the nails 

 on the second, third, and fourth digits well formed and kera- 



