Proceedings. 225 



reflecting patch the cells are arranged in many layers, the 

 number of such layers decreasing toward the periphery. At 

 the extreme edge the cells constitute a discontinuous layer, 

 consisting in fact of isolated cells on a dark ground. The 

 cells are sufficiently thin to produce interference of the 

 reflected light. The rays reflected from the isolated cells 

 and portion of the patch consisting of a single layer are 

 bluish, nearer the centre greenish, whilst still more centrally 

 the reflected light appears yellowish white. Such appear- 

 ances may be observed in the living eyes of many nocturnal 

 animals as the cat, fox, &c. 



