446 On the Rudimentary Hallux of the Kitthvake. 



advanced than those of the second, third, and fourth toes. 

 In addition to the embrj^os alluded to I have others, 

 amonnting- in all to a])out twenty specimens, and in the whole 

 of these a rudimentary hallux was present. 



In the nestling, which was well-feathered and wonld soon 

 have left the nest, a nail was found on the hind toe. When 

 sectioned this nail proved to be very hard, but similar in 

 shape and position to that on the ripe embryo. It differed 

 only in being larger and thicker, though very much thinner 

 than the claws on the other toes. 



In the adult, in which the hallux was well developed, the 

 epithelial scutes were found to be very thick and had become 

 considerably keratinized. No trace of a nail was found, not 

 even remains or aborted tissue, in the section made. 



The following is a summary of the main facts ascer- 

 tained from the examination of this limited supply of mate- 

 rial : — 



All the embryo Kittiwakes, about twenty in number, 

 possessed a hallux. 



The great majority of the immature and adult specimens 

 examined also possessed a rudimentary hallux, i. e. something 

 more than a mere tubercle. 



No nail, or traces of it, were found on the hallux or other 

 digits of embryonic specimens estimated to be twelve days 

 old, or less. 



An embryo at eighteen days had nails well developed and 

 keratinized on the second, third, and fourth digits, but 

 possessed no signs of a nail on the hallux. 



The youngest specimen with a nail on the hallux was a 

 ripe embryo. 



A well-fledged nestling and two specimens about six 

 months old possessed small scale-like nails on the hallux. 



In one case only was a nail — a very small one — found in 

 an adult specimen. 



The nail is imperfect in form and quite useless, and is thin 

 in comparison Avith the other claws on the same bird. 



Lastly, we have the ascertained position of the nail, when 

 present. The position of the nail is, I believe, unusual 



