98 



cauda a somewhat larger amount is found : 0.228 gr. The relatively 

 low CO. 2 output in the Holothurians is doubtless due to their 

 lack of extensive and rapid movements. In the experiments the 

 animals did not move at all and even in their natural environ- 

 ment they are entremely sluggish. Cohnheim also warns 

 against comparing the metabolism, measured by the CO 2 output, 

 of representatives of different groups of the animal kingdom. 

 It may be justified to compare two mammals e. g., but it is 

 absolutely impossible to compare an animal with a calcareous 

 or chitinous skeleton with a jelly fish which has only 0.24 / 

 dry weight or a Holothurian the major part of whose weight 

 is formed by the perivisceral fluid. 



The paper by Putter is doubtlessly more ,,grimdlich", but 

 I regret to say that in my opinion it contains some very 

 serious errors, which I will discuss briefly. I believe that it is 

 justifiable to give serious attention to the work of this author 

 because his conceptions on the nutrition of sea animals are so ex- 

 cedingly strange that they are either fundamentally wrong or 

 will revolutionise all our conceptions on nutrition. 



Serious criticism has also been made against his methods and 

 the ..superstructure" built by him on a very weak experimental 

 basis. While his whole theory tries to emphasise the importance 

 of dissolved C- and N-compounds as a source of food for 

 most marine animals, in all his papers we only seldom find 

 estimates of the amounts of such substances present. And the 

 few estimates he has given contain a very serious methodical 

 error as the work of Moore 87) and others has shown. 



He digests sea water with sulfuric acid for the determination 

 of the dissolved carbon. The hydrochloric acid which is set 

 free in heating sea water with sulfuric acid, is passed through a 

 wash-bottle containing lead acetate for the purpose of absorbing 

 it. This is the serious error; the acid is not only bound and 

 kept back by the lead acetate, but also sets free acetic acid 

 which after combustion is interpreted as ..dissolved organic carbon" 

 of the sea water. In his O 2 determinations an error of the same 

 kind is made in which the chlorides present in the sea water 

 are not taken into account. 



But for the present we shall take the methods of Putter as 

 methodically justified and shall confine ourselves to a criticism 

 of his theoretical considerations. 



The paper as I have said, deals with Cucumaria grubei, a 

 dendrochirote Holothurian, rather closely related in that way 

 to our Thyone. Putter first determines the general composition 

 of the animal by means of a simple, general analytical procedure. 

 The water content is 78,8 / of the total weight. 5 / of the 

 dry weight is extractive materials (inorganic salts etc.), 17.1 / 

 soluble carbohydrates, 5.6 / fats, 1.2 / lecithins, 15.8 / insolu- 

 ble carbohydrates and 55.2 / proteins. 



