316 FOUNDERS OF OCEANOGRAPHY 



Other competent observers, however, on repeating Putter's 

 experiments, have arrived at very different conclusions. 

 Thus while Putter found in the Bay of Naples as much as 

 65 to 92 milhgrammes of dissolved organic carbon per litre 

 of water, Henze in his investigation found only from 6 

 down to 3 milligrammes, and even less in some samples ; 

 and Raben, with better methods, found at Kiel, where the 

 water may be polluted, an average of about 12 milligrammes 

 per litre, and in the open Baltic only 3 milligrammes. Even 

 this, however, is a large amount of carbon compared with what 

 Putter and others state can be supplied by the plankton. It 

 must be remembered, however, that all methods of collecting 

 the smaller but immensely abundant organisms of the plank- 

 ton are still very defective, and that even the finest silk 

 nets, with which most of the data have been obtained, 

 allow a very large proportion of the nanno-plankton to 

 escape. But other estimates of the quantities of plankton 

 present are much larger than those made use of by Putter, 

 and we know that localities and seasons differ greatly. 



Piitter's other figures, in regard to the food-requirements 

 of various animals, and therefore the volumes of water 

 they must strain, have also been controverted, and some 

 of the other independent estimates of the food-requirements 

 of various animals that have been made are as follows : 



Professor E. Prince of the Canadian Sea -fisheries Depart- 

 ment states that if the sponge Suherites, one ounce in 

 weight, had such requirements that would mean nearly 

 1| billions of a Diatom like Skeletonema, or more than 7 

 biUions of Thalassiosira daily ; that similarly a Copepod 

 (Calocalanus) might require daily 9,750,000,000 Thalassi- 

 osira ; and that an oyster 5 inches long would consume 

 tV cub. in. of solid food daily, and therefore would need to 

 filter 8 or 9 gallons of water, nearly 2,000 times its 

 own bulk. Kishinouye states that the Japanese Sardine 

 would require to swim nine miles to catch the f gram of 

 food needed daily, as only one gram of Diatoms and other 



