ANIMAL LIFE OF THE DEEP SEA BOTTOM 1 65 



of the Strange features of the hermit crabs which has followed them down 

 to the deep. 



That the crabs and hermit crabs were from the bottom is beyond 

 question. But of the many prawns caught there were both species which 

 we obtained only when the trawl had been on the bottom and others 

 which we also got in the purely pelagic trawls, as described in the chapter 

 on pelagic fauna (p. 8i). The same applies to such animals as amphipods, 

 but as a rule it is not difficult to distinguish between the pale, heavily- 

 built bottom forms (Fig. p. i66) and the more delicate pelagic forms. 

 In any case it is generally true that the mode of life is transitionary, some 

 of the animals being typical bottom-dwellers, others typically pelagic, and 

 others again living freely over (but close to) the bottom and properly 

 termed abysso-pelagic. It is therefore very much a matter of experience 

 whether on board ship one decides that an animal is a bottom-dweller, 

 or near-bottom-dweller, or whether it comes from the completely free 

 water masses. 



The fishes provide perhaps the clearest example of how these life forms 

 may all be represented in a large trawl such as this, which had been 

 on the bottom but which had also fished well in the water masses on the 

 way up. 



Here in our trawl were 54 fishes spread over 21 species; but I could 

 immediately pick out eight specimens which I had never seen on the 

 world \oyage of the Dana, when Johannes Schmidt carried out pelagic 

 fishing right down to 3,000 — 4,000 metres. In our trawl there were typical 

 surface fishes like horse-mackerel (Decapterus), eel larvae, and lantern- 

 fishes (Myctophidce). There were deeper-dwelling hatchet-fishes (Stern- 

 optyx, Argyropelecus, Polyipnus) and great rarities like the tubular-eyed 

 Gigantura and Style phorus (p. 85), or the real abysso-pelagic deep-sea 

 angler-fishes (Melanocetus), and whale-fishes (Cetomimus) and many 

 others. But there remained eight fishes, six of them belonging to one 

 species, the other two representing one species each. One we had never 

 seen before, and anything resembling it had been seen only once or twice 

 before. This was at transparent, blind little fish (Fig. p. 167), in which 

 the eyes are reduced to two barely visible black pricks deep under the 

 skin. It belongs to the brotulid family, which has a few representives in- 

 shore, and even, on islands in the ^Vest Indies, in subterranean caves. These 

 last, in their blindness and colourless skin, bear some resemblance to our 

 deep-sea brotulid : it is Nature's reply to the life conditions in the perpetual 

 darkness, where other senses than sight are important, and where in the 

 struggle for existence colours are quite useless. The brotulids are the fish 



