Blackioeldtir — The Geologic Role of Phosphorus. 289 



generally tend to ever greater concentration, almost until the 

 cycle is closed upon itself. 



Soluble phosphates are absorbed by the various oceanic 

 plants as well as by those on land. In some measure the phos- 

 phoric acid becomes chemically linked in organic compounds, 

 but for the most part it probably remains in the ionized state. 

 Living diatoms and other algae contain, in both of these forms, 

 from -1 to -2 per cent of P 2 6 , chiefly as a minor constituent 

 of the cell nucleus. Although the marine animals have the 

 power of absorbing phosphoric acid directly from the sea 

 water, it so happens that they generally get a surplus of it as a 

 constituent of the plants or other animals on which they feed, 

 and hence do not exercise that power. 



The round of transformations to which phosphorus is sub- 

 jected in the ocean is extraordinarily complex. The plants 

 which absorb the element are devoured by myriads of aquatic 

 animals, each of which, in its turn, is liable to a similar fate. 

 This endless process of devouring is recognized even in the 

 ancient Chinese proverb to the effect that "the big fish eats 

 the little fish, the little fish eats the shrimp, and the shrimp 

 eats the mud." In the individual animal, the phosphorus 

 forms a constituent of its cell nuclei, tissues and liquids. With 

 the exception of casein and that of egg-yolk, the proteins do 

 not contain phosphorus, but it forms a constituent of certain 

 other organic compounds, such as lecithins. As solid calcium 

 phosphate it resides in bones, teeth and more rarely in shells. 



As phosphorus ascends in the evolutionary scale of animals, 

 its concentration tends to increase, although irregularly. The 

 protozoan, air dried, contains less than *6 per cent P 2 6 . 

 According to Juday* quantities of minute crustaceans from 

 Lake Mendota contain in the air-dried condition 1*8 to 2*4: per 

 cent of P 2 6 , or several times that of the protozoans. A Rus- 

 sian biochemist, Sempelovski, found in entire fresh specimens 

 of a cartilaginous fish (the common skate) "91 per cent P 2 6 , 

 whereas the average for eight Teleostean fishes with well- 

 developed bones was about 1*5 per cent. Certain brachiopods, 

 such as those of the family Lingulidce — form shells of fibro- 

 crystalline tricalcium phosphate — probably either the mineral 

 dahllite or staffelite. 



From its almost endless series of reincarnations in the ocean, 

 phosphorus is allowed to escape from time to time by either 

 one of two routes. The organisms in the sea may be eaten by 

 land animals, chiefly birds, or the phosphates may become 

 fixed in mineral form in the solid matter on the sea bottom, 

 and eventually buried beneath the accumulating sediments. 

 We may consider the second of these processes first. 

 * C. Juday, personal communication. 



