346 



Refractive Indices of the Eye Media. 



approximately 'T336 for aqueous, T337 for vitreous, and 1/46 for lens. 

 Determinations of the A of the aqueous humour of various animals show 

 that this is approximately the same as the A of blood serum of these 

 animals (Portier(l), Steindorff (2) ), and thus varies in the different classes 

 of animals. 



Moreover, on comparing the refractive index of the aqueous humour of 

 the sea-water Teleost (Barracouta) (l - 335) with the refractive index of the 

 sea water (1"340), it will be seen that we have here a unique phenomenon, 

 virtually the tendency to the development of a "negative eye," but, of 

 course, the almost spherical lens of refractive index about T46 will correct 

 any tendency in this direction. 



My thanks are due to Professor W. A. Osborne for his kind assistance 

 and encouragement. 



REFERENCES. 



(1) Portier, P. " Pression Osmotique des Liquides des Oiseauy et Mammiferes Marins," 



1 J. de Phys. et de Path. Gen.,' 1902, p. 202. 



(2) Kurt Steindorff. 'Handbuch d. Biochem.' (ed. by Oppenheimer), vol. 2, Part 2,, 



p. 351. 



Note on the Iridescent Colours of Birds and Insects. 

 By A. Mallock, F.B.S. 



[This paper is published in Series A, No. 582 (vol. A 85, pp. 598—605).] 



