Af 



A vaet -amount of work remains to be done before even an 

 approximately adequate picture can be gained of the regularly 

 periodic and regional variations in the amounts of the rarer suo- 

 stancej in the sea water. But growing realization of the importcnce 

 of these in the life cycle in the sea raakes this a task so pressing 

 that a considerable nu.^ber of institutions are devoting their efforts 

 thereto both in Anerica and Europe. As knov/ledge increases, first 

 one and then a.nother of these rare substances move to be of vital 

 irD],^orbance. At the present time attention in this field centers 

 chiefly around the concentration of phosphates, of nitrates, of 

 silicates, and of the salts of a.Ti-aonia. Adequate methods have 

 already been developed to measure the araounts of some of these in 

 tne water. But we still lack a satisfactory technique for deter- 

 mining, with sufficient accuracy, the actual amounts of nitrates 

 that are present in solution. And as attention becomes focused on 

 other solutes, other developments of technique will be needed, 

 because chemists have, in this case, to do v/ith solutions so 

 attenuate that they are close to the lower limit at which accurate 

 analysis is possible. In fact, some of the rare substances are 

 known to exist in sea water only because they have been detected in 

 the bodies of marine animals and plants, which could only have ob- 

 tained them from their aqueous environment, illustrating the delicacy 

 of procedure that would be necessary to measure them in the water. 



Recent observations have also led oceanographers to turn their 

 attention afresh to the regional variations in the amounts of oxygen 

 and of nitrogen-gas in the water, as indices to various physical and 

 biological events there. Here again the immediate need is for 

 thorough regional and bathymetric survey for this alone can give a 

 sufficiently descriptive picture of the existing state, 



D. LIFE III THE SEA 



'JlTIiile study of whatever manifestations or activity of liie in 

 the sea is a part of the fundamental science of Biology, differences 

 in the disciplines employed, and in the nature of the irmriediatc 

 problems attacked, make it convenient to classify this branch of 

 science under three headings: (1) Oceanic Biology, (2) Marine 

 Physiology, (3) Marine Bacteriology. 



The first of these is chiefly concerned with the ways in v/hich 

 the basic conditions of life in the sea are made manifest by the 

 diversity in structure and in habits of animals and plants. This 

 includes such subjects as Taxonom.y and its relation to geographic 

 and bathyiiictric distribution; the dependence of successful reproduc- 

 tion, growth, migrations, etc., on definite factors in the marine 

 environment, including the general subject of life histories; the 

 adaptations tha-t enable various groups to populate particular parts 

 of the sea; the interdependences of species of animals, and of 

 animals as a group of plants; the environmental factors that govern 

 plant growth; and all problems in cognate fields. 



Marine Ph^^siolog^i^ covers the study of the general and basic 

 conditions and phenomena of life that are common to marine ani:7i3.1s 

 and plants; study of the vital reactions between the cell, or 

 aggregate of cells, and the external environment; and the intjr- 



