FISHES 



297 



Figs. 3:28 and 329. — Thk Chokoidal Gland of the Trout, Salmo trutta 

 (Xorman Ashton). 



Fig. 328. — The " gland " occupies the upper part of the figure ( X SO). 



Fig. 329.— Structure of the -'gland" ( X 320). 



it is possible that it serves a protective disguise in tloe transparent larva 

 the black eyeball of which would otherwise be dangerously conspicuous, 

 blending with the reflexes of the water m the same way as do the silver 

 reflections from the sides of the adult fish. In a few^ species there is, 

 in addition, a tapetum fibrosum on the inner aspect of the choroid 

 separating the main vascular layer from the choriocapillaris, such as is 

 typical of hoofed Mammals (Millot, 1923) ^ : it is composed of a layer 

 of dense fibrous tissue of a glistening tendon-like structure wherein the 



' p. 457. 



