506 CYCLES OF ORGAXIC AND INORGANIC SUBSTANCES 



have been obtained by my colleague Dr. Johnston (1959), by the 

 use of antimetabolites, as to the metabolic requirements of several 

 species. To me, it has always seemed that one approach to this 

 problem lies in the use as media of filtrates of organisms known to 

 grow earlier in the succession, and more might be done in this 

 manner. Any successes could be followed by rigorous chemical 

 analysis or bioassay. That, howe\'er, is merely a suggestion. What 

 is certain is that work of these kinds is fundamental to most of 

 the other lines of investigation. In conjunction goes an urgent 

 need for more work in the field of marine bacteriology (and 

 mycology, for exarrple, see Vishniac, 1956), and in the effects on 

 bacteria of algal (or fungal) metabolites, and vice versa. 



2, Then, or rather in association, there is the essential work in 

 the field — what is significant and the vital questions of how often 

 and how much. We are only just beginning on this task at the 

 ectocrine level (e.g., Wilson, 1958; Johnston, 1955; Cowey, 1956; 

 also various contributors to the afternoon sessions of this Congress), 

 and know little enough at the nutrient level! It will require very 

 careful selection of projects if progress is to be made economically, 

 and standardizing of methods between workers and countries (e.g., 

 Daisley, 1959). Doubtless some of the laboratory results will prove 

 to be illusory or irrelevant, and others less important in vivo than 

 they can be in viiro. This possibility exists even for B12 (e.g., Droop, 

 1957 ; Vishniac and Riley, 1959), but there is no doubt that relevant 

 evidence will be found. As an example, I may mention another part- 

 time investigation by Dr. Johnston. From a number of cruises he 

 has obtained groups of sea water samples, for special filtration and 

 standard nutrient additions, so that their essential differences 

 should lie as far as possible only in their dissolved organic contents. 

 When used as media for subculture of laboratory algae (cf. John- 

 ston, 1955), differential growths were obtained, and this alone will 

 not be surprising. But, although his results are still only interim 

 and cannot as yet be said to be reprcducible, the interesting thing is 

 that for a few routine cruises these differential results grouped 

 themselves into suggestive spatial patterns, and not at random. 



3. In particular, by its very nature, such work leads logically 

 to progress in the tantalising field of ecological success and suc- 

 cession, obviously in the phytoplankton and perhaps also in the 



