32 president's address. 



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

 the cod, which is almost destitute of fat. 



Professor Brandt, at Kiel, Professor 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 Dinoflagellates, or of Copepoda. And, no doubt, 

 the animals of the ' benthos,' the common invertebrates of our shores, 

 will show similar differences in analysis.^" It is obvious that some 

 contain more solid flesh, others more water in their tissues, others 

 more calcareous matter in the exoskeleton, and that therefore weight 

 for v/eight we may be sure that some are more nutritious than the others ; 

 and this is pi'obably at least one cause of that preference we see in 

 some of our bottom-feeding fish for certain kinds of food, such as 

 polychaet worms, in which there is relatively little waste, and thin- 

 shelled lamellibranch molluscs, such as young mussels, which have a 

 highly nutrient body in a comparatively thin and brittle shell. 



My object in referring to these still incomplete investigations is to 

 direct attention to what seems a natural and useful extension of faunistic 

 work, for the purpose of obtaining some approximation to a quantitative 

 estimate of the more important animals of our shores and shallow 

 water and their relative values as either the immediate or the ultimate 

 food of marketable fishes. 



Each such fish has its ' food-chain ' or series of alternative chains, 

 leading back from the food of man to the invertebrates upon which it 

 preys and then to the food of these, and so down to the smallest and 

 simplest organisms in the sea, and each such chain must have all 

 its links fully worked out as to seasonal and quantitative occurrence 

 back to the Diatoms and Flagellates which depend upon physical con- 

 ditions and take us beyond the range of biology — but not beyond that 

 of oceanography. The Diatoms and the Flagellates are probably more 

 important than the more obvious sea- weeds not only as food, but also 

 in supplying to the water the oxygen necessary for the respiration 

 of living protoplasm. Our object must be to estimate the rate of pro- 

 duction and rate of destruction of all organic substances in the sea. 



To attain to an approximate census and valuation of the sea — 

 remote though it may seem — is a great aim, but it is not sufficient. 

 We want not only to observe and to count natural objects, but also 

 to understand them. We require to know not merely what an organism 

 is — in the fullest detail of structm''e and development and affinities — 



'"' Moore and others have made analyses of the protein, fat, etc., in the soft 

 parts of Sponge, Ascidian, Aplysia, Fusus, Echinus and Cancer at Port Erin, 

 and find considerable differences^the protein ranging, for example, from 8 to 

 51 per cent., and the fat from 2 to 14 per cent, (see Bio-Chemical Jown. vi. 

 p. 291). 



