io SCIENCE PROGRESS 



circulated is sufficient for these requirements. It does not 

 appear to me, when Putter's experiments are considered, that 

 this view is at all tenable. The actual amount of oxygen, 

 carbon, and nitrogen exchanged between the sponge Suberites 

 domnncula and its surrounding water was determined by 

 Putter, 1 and it was found that for an animal of about 60 grammes 

 in weight, and about 60 c.c. in volume, this interchange per 

 hour was : 



C92 mg. of carbon, and 

 0"0i38 mg. of nitrogen. 



Let us suppose, for the moment, that these amounts of 

 carbon and nitrogen are to be obtained from plankton organisms. 

 It is then necessary that we should know what are the propor- 

 tions of such food substances present in the sea, and available 

 for those animals which presumably utilise them as food. 

 What quantity of plankton then was present per unit volume 

 of the water of the Bay of Naples (where Putter made his 

 experiments) ? The results of the latter would have been more 

 satisfactory if quantitative plankton observations had been 

 carried on concurrently with the metabolic researches. Such 

 observations were carried out by Schiitt and Apstein 2 (1888-96), 

 but they were made by means of the Hensen vertical net, and 

 it appears from the investigations of Lohmann 3 that this 

 apparatus does not present us with an accurate picture of the 

 contents of the sea so far as the smaller planktonic organisms 

 are concerned. The only results which can be applied are 

 those obtained by Lohmann 3 in a series of experiments made in 

 the open Mediterranean off Syracuse, and these are of particular 

 value since they were made by various methods, and probably 

 represent very approximately the total contents of the sea 

 in situ in organised food substance. It is indeed possible that 

 the abundance of plankton in the Mediterranean off Syracuse 

 may differ from that in Naples Bay, but we shall see that a 

 considerable difference may be assumed without affecting the 

 conclusions to be drawn. Lohmann found as the results of 

 an exceedingly careful series of plankton fishing experiments 



1 Vergl. Phys. Stoffiv. p. 43. 



2 Summarised by Brandt in " Stoffwechsel im Meeres," Wissensch. Meeres 

 untersuch. Kiel Kommission, Bd. vi. Abth. Kiel, 1906. 



3 " Neue Untersuch. Reichthum d. Meere an Plankton," ibid. 



