The Biologist Poses Some Problems 



G. E. HUTCHINSON 



Department of Zoology, Yale University, 

 New Haven, Connecticut 



THIRTY years ago the role of a biologist in a symposium of 

 this kind woulci have appeared both simple and illuminating. 

 Macallum's (1926) ideas on the chemistry of the blood of fresh- 

 water vertebrates were widely accepted, the huge span of pre- 

 Cambrian time was unappreciated, so that the earth appeared 

 much younger than it does now, and the obvious conclusion that 

 by analyzing the blood of teleosts we could get the composition of 

 the middle Paleozoic seas remained unchallenged. 



In 1931 Pantin published a skeptical essay on the matter, and 

 in 1942-43 came Conway's fundamental papers w^hich demolished 

 completely the older views. Conway (1942, 1943) showed that at 

 least throughout Phanerozoic times there can have been very 

 little change in the concentration of the major ions of sea water. 

 Only in a few cases, notably in that of strontium, can we hope for 

 direct evidence of ionic ratios, and even in this one case there is 

 considerable uncertainty among different investigators as to 

 whether a significant change has indeed taken place. The indirect 

 arguments used by Conway, however, seem so compelling that in 

 the absence of any clear contrary evidence we may assume that 

 during the period for which we have good fossil evidence the sea 

 has remained very much the same in overall chemical composition. 



The differences between sea water and cell or body fluids appear 

 now to be related in part to the evolution of various biochemical 

 mechanisms in which ions have a function, and in part to the 

 history not of the ocean but of animals which can migrate from 

 salt to freshwater and back again. It might, therefore, appear 

 that the biologist has little to offer even in the process of framing 



85 



