INTRODUCTION. II 
physiological type. Among birds the horned puffin 
(Fratercula corniculata) will be selected. 
Growing from the upper eyelid of this bird is a 
slender, pointed, black-coloured horn, which in the 
specimen from which the drawing (fig. 7) was made 
measured eighteen millimetres in length: there is also 
) 
a thin horny scale connected with the lower lid. In 
the adult bird it is stated that these horns are shed and 
reproduced annually. 
Fic. 7.—Head of the Horned Puffin (/atercula corniculata) 
to show the horn growing from the upper eyelid. 
It has already been mentioned that the corneous cap 
of the cavicorn ruminants is merely modified portions 
of the integument. In the Prongbuck (Axzclocarpa 
americana) the hard cap of the horn is annually shed, an 
observation first made in 1865 in the Zoological Gardens, 
London. Subsequently, doubt was thrown on_ the 
matter, but it has been definitely settled by the observa- 
tions of Mr, W. A. Forbes. Thus we are able to furnish 
