36 THE DEPTHS OF THE SEA 



variety in their otherwise sombre appearance. Many 

 of the fishes, however, present a gayer clothing. Some 

 are violet, others pale rose or bright red. Others have 

 a white almost translucent skin, through which the 

 blood can be seen and its course traced even in its 

 finer vessels. Purples and greens abound amongst 

 the holothurians ; other echinoderms are white, 

 yellow, pink, or red. Red is, perhaps, the pre- 

 dominant colour of the Crustacea, though it has been 

 suggested that this colour is produced during the long 

 passage to the surface, and that some of the bright 

 reds which we see at the surface are unknown in the 

 depths. Violet and orange, green and red, are the 

 colours of the jelly-fishes and the corals. 



It thus appears that there is a great variety and a 

 great brilliancy amongst many of the bottom fauna. 

 With the exception of blue, all colours are well repre- 

 sented ; but the consideration of one or two facts seems 

 to show that colour plays little part in their lives. 

 Apart from the fact that to our eyes, at any rate, these 

 gorgeous hues would be invisible in the depths, it is 

 difficult to imagine that each of these gaily-coloured 

 creatures can live amongst surroundings of its own 

 hue. Again, it is characteristic that the colour is 

 uniform. There is a marked absence of those stripes, 

 bands, spots, or shading which play so large a part 

 in the protective coloration of animals exposed to 

 light. Although there is no protective coloration 

 amongst the animals of the deep sea, the luminous 

 organs, which make, for instance, some of the cuttle- 

 fishes as beautiful and as conspicuous as a firework, 

 may, in some cases, act as warning signals. Having 

 once established a reputation for nastiness, the more 

 conspicuous an animal can make itself the less likely 

 is it to be interfered with. One peculiarity connected 

 with pigment, as yet inexplicable, is the fact that, in 

 deep-sea animals, many of the cavities of the body are 



