104 STUDIES IN INSECT LIFE, ETC. 



ultra-violet rays already predominated. At 250 

 fathoms the effect of the red and green rays was 

 imperceptible even after a long exposure of plates 

 especially prepared to register them. The ultra- 

 violet and the blue rays are those which penetrate 

 deepest. These records correspond closely with 

 the observations of Hermann Foil in his diving 

 expeditions in the Mediterranean. At a depth 

 of 15 fathoms dark red animals looked to him 

 quite black, whilst the green and blue-green algae 

 appeared lighter in colour. A coloured object of 

 course looks black when untouched by rays of its 

 own colour. In accord with this absence of red 

 rays below 250 fathoms we find a very large 

 number of Crustacea, some of them of consider- 

 able size, and all of a most brilliant red colour- 

 scarlet as a boiled lobster swimming about in 

 the seas just below the lower limit of the pene- 

 tration of the red rays. As a rule, however, in 

 this region the fish are black in colour, though 

 closely allied species of the same genus, variegated 

 and light in hue, are swimming about in the upper 

 waters. 



Not only is there no light, but there is no sound 

 at the bottom of the sea except for the rare 

 explosion of a submarine volcano, and even when 



