55 



very dim light, or of darkness, and so have developed no adaptive 

 physiologic protection against the lethal or other metabolic effects 

 of the whole of the sun's spectrum, or of any part of the latter. 

 This in turn, lends to the very interesting problem of luminescence, 

 so highly developed a'flong marine animals. 



The physical simplicity of the marine environment also opens to 

 the investor many promising lines of attack upon the problems center- 

 ing around the widely diverse functions of the different classes of 

 organic substances that we group together as "pigments", simply 

 because they chance to possess absorption bands falling within the 

 region of wave frequency to which the human retina is sensitive, 

 which does not necessarily mean that they are similar ?ither chemi- 

 cally or vitally. 



The basic nature of the respiratory pigments, for example, is a 

 subject that has hardly been touched on as yet, from the standpoint of 

 specific differences within a given group of animals, or of larger 

 differences between different groups. Crustacea, worms and fishes 

 especially lend themselves to investigation h^re. For example, study 

 of the qualities rith respect to oxygen of the compounds, that in 

 lower animals, a.re analogous to haemoglobin in the higher, may lead to 

 better understanding of the blood physiology of raajr-mals, and so of 

 man. Respiratory pigments are only one of a great number of sub- 

 stances that cry for study from this point of view. In fact, the 

 whole relationship between chemical composition end systematic rela- 

 tionships ejTiong different groups of animals and plants is still a 

 practically virgin field, and one offering most fertile possibilities 

 to the marine physiologist. 



Carrying the chain a. link further, what is the oxidation-reaction 

 mechanism of the pigments of the marine and fresh-water animals, such 

 as the green Serpulids, the Sipunculids, etc., and the plankton 

 inhabitants (belonging to many groups) of the mid-depths of the North 

 Pacific that live in very lew oxygen tensions? a large number of 

 marine bacteria are also colored. Do these pigments also possess 

 oxido-reductive power? 



This introduces us to the still more basic problem of photo- 

 synthesis, an energy capturing process in which, so far as we now 

 know, certain pigments invaria.bly play an active role. This, it is 

 true, is not specifically a marine problem, but it is in the marine 

 environment that photosynthesis shows its greatest variation, for in 

 the ocean the pigments concerned with photosynthesis are developed in 

 greatest diversity. An intensive study of the properties of these 

 pigments, chemical, physical, and physiological, is one of the major 

 tasks that now faces the general physioloQ-ist ; a task whose accom- 

 pli ehraent would throw light on our present ignorance of th=^ ways that 

 solar energy is turned to the service of living beings en our clanet. 



It is not necessary to list more examples, for there is gen-ral 

 agreement as to the opportunity that marine organisms, in their sea- 

 water environment, offer the comparative physiologist. But for him 

 to make the most of these opportunities (and especially in America) 

 has heretofore been difficult, chiefly because the problems are tech- 

 nically too elaborate to be successfully attacked as isolated projects 



