142 Royal Society : — 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAL SOCIETY. 



May 16, 1872.— Francis Galton, M.A., Vice-President, in the Chair. 



" Remarks on the sense of Sight in Birds, accompanied by a de- 

 scription of the Eye, and particularly of tlie Ciliary Muscle, in three 

 species of the order Rapaees." By Robert James Lee, M.A., 

 M.D. 



It is proposed in this communication to describe certain peculiarities 

 in the eye of the bird as compared with the eyes of other Vertebrata, 

 and, further, to examine to what extent those peculiarities enable us 

 to explain the remarkable powers of sight with which all species of 

 birds are more or less highly endowed. 



Those who study the haijits and modes of existence of the lower 

 animals, find great interest in applying to various phenomena con- 

 nected with them the results of anatomical investigation, and in 

 endeavouring to discover such causes, or means adequate to produce 

 such effects, as to render the supposition of the existence of an 

 indefinite property like instinct very frequently unnecessary. 



This method it is my desire to apply in the explanation of those 

 high and distant flights which are performed by certain species of 

 birds in search of food or in their migrations to different localities. 



For us it is difficult to form a clear conception of the power of 

 sight possessed by birds if we only use our own faculties in this 

 respect as the standard of comparison ; by which I mean to imply 

 that the mind must be prepared for the consideration of the pheno- 

 mena referred to by observing in detail numerous important differ- 

 ences in the structure of the eye, which combine to facilitate a 

 conception of ideas otherwise beyond the reasonable limits to which 

 even imagination might extend. 



This field of inquiry will long engage the attention of the naturalist 

 and anatomist ; indeed it may be said to be inexhaustible ; and I 

 feel considerable hesitation in offering a contribution insignificantly 

 small to the elucidation of a subject of such magnitude. 



We may acquire some idea of the sight of the bird by comparing 

 the dimensions of the eye with those of the brain or the optic lobes ; 

 and by arranging the measurements thus obtained, and referring 

 them to some fixed standard, we may estimate the relative and 

 individual powers of vision enjoyed by different species. In illustra- 

 tion of this we have an instance, in the case of one of the birds which 

 I propose to describe minutely in this communication, in which the 

 eye is actually considerably larger than in the human species ; and 

 we have a still more striking example, considering the size of the bird, 

 in the Goura coronata. 



Again, if we regard the eye as an optical instrument, we may 

 estimate its efficiency by examining the internal structures on which 

 the formation and perception of the image depend, — such as the 



