266 POPULATION'S OF THE SEA 



migrations of this sort down to such depths. (2) Very recent 

 investigations indicate that there is a great variety of heterotrophic 

 plants in the aphotic zones of the oceans: bacteria, yeasts, fungi, 

 and flagellates (ZoBell, 1946; Kriss, 1959; Hohnk, 1952-1956; 

 1959). What about their ability to synthesize vitamins? We 

 do not know. Perhaps they are autochthonous producers in the 

 deep sea. (3) In connection with the cartilaginous nature of 

 skeletons of deep-sea animals it must not be forgotten that 

 physlcochemical conditions in deep water are quite different from 

 those near the surface. For example, Wattenberg in the 1930's 

 (1933; 1936) reported that dissociation of carbonic acid is increased 

 by hydrostatic pressure and that therefore the solubility of 

 calcium carbonate is increased. This means that deposition of 

 calcium carbonate by organisms is greatly reduced. 



The second phenomenon to be mentioned is the part light plays 

 in the radiation "climate." Its importance in evolution is quite 

 another chapter in marine biology. 



Summarizing, we see that illumination beneath the sea surface 

 by light from both the sun and moon is extremely important in 

 various biological phenomena in its intensity, in its spectral 

 composition, its effect in combination with other factors such as 

 temperature, the salt content or fluorescent substances, and its 

 role in productivity, in the synthesis of vitamins, and finally in 

 evolution. One must conclude that our knowledge of light in the 

 sea must be increased markedly in order to analyze and to under- 

 stand a great many different biological processes in the sea. It 

 provides a wide field for cooperation between physicists, chemists, 

 and biologists, as is true in many other problems in oceanography. 



REFERENCES 



References with an asterisk contain more bibliographic material. 



Abbott, B. C, and D. Ballantine. 1957. The toxin from Gymnodinium 



veneficum Ballantine. /. Marine Biol. Assoc, United Kingdom, 36, 



169-189. 

 Burdon-Jones, C, and G. H. Charles. 1958. Light reactions of littoral 



gastropods. Nature, 181, 129-131. 

 Clarke, G. L. 1936. On 'the depth at which fish can see. Ecology, 17, 



452-456. 



