258 



PROF. W. A. HERPMAN OX THE ABUNDANCE 



metabolism or domestic economy of the sea — the computing of income and 

 expenditure so as to find out whether we have a balance to the good, and 

 whether the sea could be made by further cultivation to produce still more 

 food for the service of Man. 



Conclusions. 



From these and similar data which can be readily obtained, it is not 

 difficult to calculate totals by estimating the number of square yards in areas 

 of similar character between tide-marks or in shallow water. And from 

 weiohings of samples some approximation to the number of tons of available 

 food may be computed. But one must not go too far. Let all the figures 

 be based upon actual observation. Imagination is necessary in science, but 

 in calculating a population of even a very limited area it is best to believe 

 only what one can see. 



Countings and weighings, however, do not give us all the information we 

 need. It is something fo know even approximately the number of millions 

 of animals on a mile of shore and the number of millions of tons of possible 

 food in a sea-area, but that is not sufficient. All food-fishes are not equally 

 nourishing to man, and all plankton and bottom Invertebrata are not equally 

 nourishing to a fish. At this point the biologist requires the assistance of 

 the physiologist and the biochemist. We want to know next the value of 

 our food matters in proteids, carbohydrates, and fats, and the resulting 

 calories. Dr. Johnstone, of the Oceanography Department of the University 

 of Liverpool, has already shown us how markedly a fat summer herring- 

 differs in essential constitution from the ordinary white fish, such as the cod 

 which is almost destitute of fat, as follows: — 





Herring. 



Cod. 





21 



22 



9 



48 



16-7 

 0-3 

 1-3 



81-7 



Fats 



Ash (+ salt) 







Prof. Brandt, at Kiel, Prof. Benjamin Moore, at Port Erin, and others, 

 have similarly shown that plankton gatherings may vary greatly in their 

 nutrient value according as they are composed mainly of Diatoms, of Dino- 

 flaoellates, or of Copepods ; and Prof. Moore has kindly analysed for me, 



