March 24, 1911] 



SCIENCE 



461 



with his theories and the present volume is a 

 ■welcome contribution because Dr. Piitter gives 

 a more detailed presentation of his views and 

 replies to the more important objections 

 offered by his critics. 



The first chapters are preparatory to the 

 discussion of the chief topic, i. e., how aquatic 

 animals obtain an adequate supply of food. 

 They deal with such questions as the intensity 

 of metabolism in the various groups of aquatic 

 animals, the food requirements of these ani- 

 mals, the different types of food of various 

 groups, including both vertebrate and inver- 

 tebrate forms, and the source of organic sub- 

 stances dissolved in the water. The view is 

 presented that the estimation of the food re- 

 quirement of an animal should be based upon 

 the area of active absorbing and secreting 

 surfaces, more especially the effective respira- 

 tory surface, rather than upon the mass, be- 

 cause the oxygen consumed is a good measure 

 of metabolism, and the rate of consumption of 

 this gas shows the intensity of this process. 

 Calculated on this basis, the author finds that 

 the food requirement of many aquatic animals 

 has been greatly underestimated hitherto and 

 that the total demand in a body of water is 

 frequently greater than the supply of organ- 

 ized food which is produced by it. One in- 

 stance is cited in which the demand for food 

 by the zooplanktonts of a body of water ex- 

 ceeded the supply of organized food for nine 

 months out of a period of thirteen, and in 

 another instance demand exceeded supply for 

 each of thirteen months. Naturally, this ex- 

 cess of demand over supply raises the question 

 as to how this deficit is made good and the 

 author's answer to this query is his important 

 contribution to the subject under discussion. 



Dr. Putter maintains that aquatic animals 

 have recourse to the organic substances which 

 are always found in solution in natural waters, 

 and in this way the deficiency is supplied. He 

 asserts, in fact, that these dissolved organic 

 substances which are generally present in 

 amounts varying from ten milligrams to 

 twenty milligrams per liter of water are not 

 only drawn upon in emergencies, hut that they 

 are the chief source of the food of some forms. 



With respect to the ability of aquatic ani- 

 mals to make use of dissolved food an experi- 

 ment by Knorrich is cited in which Daphnes 

 survived for a period of fourteen days on a 

 diet consisting solely of dissolved food. The 

 author himself found that goldfish lived for a 

 period of forty-one days in tap water which 

 contained no organized food and the oxygen 

 consumed substantially accounted for the loss 

 in weight; but when organic substances were 

 dissolved in the tap water, the goldfish sur- 

 vived for seventy-eight days, nearly twice as 

 long, and the oxygen consumed greatly ex- 

 ceeded the amount that would account for the 

 loss in weight. The conclusion drawn from 

 this experiment is that these goldfish were 

 able to make use of the dissolved food, because 

 they lived so much longer when supplied with 

 this kind of food than when given neither 

 dissolved nor solid food, and because of the 

 extra quantity of oxygen consumed. 



Solid food is not regarded as a thing which 

 may be dispensed with entirely, but dissolved 

 food may play a more or less important role, 

 even to the point of being the chief source of 

 food for some organisms, such as sponges, 

 which frequently appear to receive very little 

 in the way of organized food. 



Dr. Piitter's conclusions are not always con- 

 vincing and there is a paucity of evidence in 

 some instances which serves to show how re- 

 cently this field has been invaded by investi- 

 gators; but the views expressed are suggestive 

 and will doubtless stimulate investigations in 

 this field of research and eventually result in 

 giving us a much better knowledge of the 

 nutrition of aquatic animals. 



C. JUDAY 



TEE AMEBIC AN ASSOCIATION FOB TEE 

 ADVANCEMENT OF SCIENCE 

 SECTION E 

 The regular annual meeting of Section B of 

 the American Association for the Advancement 

 of Science was held in Pillsbury Hall, University 

 of Minnesota, December 27, 28 and 29. A pro- 

 gram of papers was read both morning and after- 

 noon each day. Due to the unavoidable absence 



