External metabolites in the sea 1 45 



neighbourhood (as had been usual) and (b) water collected from the Celtic Sea, in 

 which the typical plankton community is normally similar to that of the " local " 

 water before 1931. The results were striking; good growth of polychaete and 

 echinoderm larvae was obtained in the latter and only poor or deformed growth in 

 the former. Appropriate combinations of experiments suggested the presence of a 

 " beneficial " substance in the Celtic water, and its lack in the local water, rather than 

 the existence of a harmful substance in the latter. More recent work has shown that 

 Clyde water also tends to be more suitable than " local " Channel water and, although 

 there are variations, the inferences seem to be unambiguous. In association, Wilson 

 and Armstrong (1954) have shown that heating the waters for shorter or longer 

 periods generally had an adverse effect on the larvae bred in them, thus suggesting 

 the existence of a beneficial substance of a more or less volatile nature. Their analyses 

 have not yet been carried to the stage of demonstrating any particular component 

 or fraction which is responsible for the biological difference. 



Recently, at Aberdeen, Johnston has extracted various fractions of the organic 

 matter in natural sea waters, and made some preliminary biochemical analyses. 

 Certain of these were tested in bio-assay on a number of phytoplankton diatoms and 

 flagellates (with results summarized by Johnston in his Table I, 1955, from a paper 

 read to the International Council for the Exploration of the Sea in 1954). It was found 

 that the growth of many was favoured and of some others hindered relative to controls, 

 although, " since the tests were limited to one concentration, further (and perhaps 

 different) instances of these effects would probably have been observed by testing a 

 range of concentrations. One particular fraction was found to promote greater growth 

 in 9 of the 1 1 species tested." The initial information so gained is providing a basis 

 for the bio-assay of sea water samples from different areas, with a view to a preliminary 

 labelling of such waters according to their physiological effects. Then, further attention 

 will be given as far as possible to identifying some of the substances thus found to be 

 of biological significance. Johnston tentatively discusses the possible value of such 

 information to the fisheries worker. 



In all such experimental work, tribute should be paid to the surveys made by 

 Russell (e.g., 1939) and Fraser (e.g., 1952). By distinguishing on biological evidence 

 between water masses, which have often been indistinguishable on familiar hydro- 

 graphical criteria, they are providing the experimenter and biochemist with invaluable 

 clues. 



In conclusion, it can be said that, before the war, a few people were moving towards 

 a conception of ecological inter-relationships which seemed likely to be an important 

 complement to the already familiar relationships existing between the organism and 

 its physical environment, and those between prey and predator. Limited observations 

 in diverse fields suggested that these non-predatory relationships would be mediated 

 by the release of metabolites of varying potency for other members of the community. 

 Further work during the war made it possible to gather much more support for the 

 suggestion, and it is now quite clear that dissolved or colloidal organic matter may be 

 present in natural fresh and marine waters in greater quantities than was originally 

 envisaged. Indeed, it is still uncertain whether these may not in themselves provide, 

 for some forms, nutrients in the ordinary sense of the word*. It is also clear that within 



*See, for example, Morris, 1955. 



