FOOD-MATTERS IN THE SEA 315 



metabolism of other organisms — such as the algee of the 

 plankton, and the other larger marine algae. Putter based 

 this conclusion upon figures which he published showing 

 that there was a surprisingly large amount of dissolved 

 organic carbon in the sea-water of the Bay of Naples, 

 where his work was carried out, and that the nutritive 

 requirements of some of the higher marine invertebrate 

 animals could not be met by the amount of lower organisms 

 (the plankton) contained in the volume of water available 

 for their use. 



Taking certain common marine animals — he calculated 

 from the consumption of oxygen the minimal value of the 

 carbon required per unit of time for an animal of a given 

 body weight, then taking certain figures for the amount of 

 plankton strained from a given volume of water (by Lohmann 

 ofi Syracuse, during December) he calculated the amount 

 of water that the animal in question would require to strain 

 in order to obtain the required carbon, and declared it to 

 be an impossibly large amount. For example : In the 

 case of the common marine sponge Suherites domuncula at 

 Naples, he calculated that with a body- weight of 60 grammes 

 (about 2 oz.) it required 0*9 milligrammes of carbon per 

 hour. Taking Lohmann's results as to the plankton in the 

 Mediterranean it followed that the sponge, in order to 

 obtain that amount of carbon from the plankton, would 

 require to filter 242 Htres of sea-water per hour — about 

 4,000 times its own volume. This amount of water he 

 showed could not pass in the time through the openings and 

 water passages of the sponge. On the other hand, he finds 

 that the sea-water he analysed contains sufficient of the 

 dissolved organic-carbon compounds to supply the needs 

 of the sponge from an amount of water that could easily 

 pass through the sponge cavities in an hour. He obtained 

 similar conclusions in the case of the Holothurian Cucumaria 

 gruhei, and subsequently extended his investigations to an 

 ascidian, a sea-anemone and a fish, with like results. 



