ANIMAL LIFE IN THE SEA 179 



is that in the daytime it hves at about 300 fathoms, 

 but at night it rises to within 80 fathoms of the surface. 

 Its young are crystal clear, and are surface forms living 

 in the upper 80 fathoms. On the other hand, some 

 members of the genus Alepocephalus Hve as far down 

 as 1,100 fathoms, and have no Mght organs. Their 

 young are the same black colour as the parents, and 

 live also in the great depths. 



To sum up, so far as we know at present, forms 

 which live in the surface waters of the ocean are crystal 

 clear or pale violet or blue. Those which live in layers 

 where only blue and violet rays penetrate freely tend 

 to be silvery and to have large eyes and large Mght 

 organs. Still deeper, where no red and no green rays, 

 even in some instances no rays at all, penetrate, the 

 colour becomes red or black, and light organs are small 

 or disappear. That there is an intimate relation between 

 the characters and colouring of the orgajiism and the 

 amount of Hght present is shown by the fact that when 

 the larva inhabits the same depth as the parent it has 

 the same colours. When it inhabits another zone it 

 takes on the normal colouring of the inhabitants of 

 that zone. Further, the fact that the forms from 

 deeper water occur in different layers of water in 

 different latitudes — the level corresponding to the 

 degree of penetration of light in the particular latitude, 

 so that the animals Mve higher up in high latitudes 

 than ia low — suggests that the life of the animals is 

 strongly influenced by the amount of light present. 



One other point is interesting in regard to the life 

 of these depths. Just as the littoral fishes often send 

 pelagic larvae out to the open sea, so some of the 

 abyssal fishes seem to have bathypelagic larvae, i.e. 

 larvae living in the open water, but at considerable 



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