RE. , iKATORY EXCHANGE IN DIFFERENT ANIMALS 137 



pears to be approximately constant. The exchange per unit surface 

 is increasing in Carmarina, approximately constant in Beroe\ but de- 

 creasing in Rhizostoma and Cestus. 



Montuori [1913] has made a large number of determinations (242) 

 on eighty different species of marine animals (fish, molluscs, Crustacea, 

 worms, echinoderms and Coelenterata). All the experiments were 

 made at a constant temperature, but the animals were free to move 

 about. Many of them were very quiet however. The results are 

 extremely irregular, and, as in most cases very few experiments have 

 been made on each species, valid conclusions cannot be arrived at 

 with regard to these. On each of eleven species five or more deter- 

 minations have been made. Seven of these series are too irregular to 

 be of much value, while four are fairly regular. Of the seven, three 

 (the crustacean Pachygrapsus marmoratus, the mollusc Lithodomus 

 lithofagus, and the eel Anguilla vulgaris) show on the whole a decrease 

 of the respiratory exchange per unit weight with decreasing size, 

 three give results which appear to be independent of the size (Ascidia 

 mentula, Mugil cephalus. Torpedo ocellata), and one only (Urano- 

 scopus scaber) shows increasing metabolism with decreasing size. Of 

 the four which give fairly regular results the three (Beroc Forskali, 

 Holothuria impatiens, Sepia officinalis) have a metabolism per unit 

 weight which is independent of the size, while Carcinus mcenas alone 

 shows an increase with decreasing size. The results obtained on the 

 eight last-named species have been reproduced in Table XXVIII and 

 figures for the metabolism per unit surface added. 



If any general conclusion can be based on Montuori's results it 

 must be, as Montuori himself thinks, that the metabolism is propor- 

 tional to the weight and not to the surface, but it is certainly safer 

 not to be emphatic on the point. It should be borne in mind that 

 there is at present no valid reason for assuming a priori that the 

 same rule should hold with regard to all cold-blooded animals. 



THE THEORY OF THE " SURFACE LAW ". 



Bergmann [1848], Regnault and Reiset, and especially Rubner 

 [1883], have tried to bring the observed relation between the size and 

 the respiratory exchange of warm-blooded animals into correlation 

 with their heat loss. Other things being equal, the loss of heat is pro- 

 portional to the surface of an animal, and, according to Rubner, the 

 metabolism is simply a function of the conditions for loss of heat, 

 while there is no such thing as a specific oxidative activity of the cell. 

 This view and the theory of direct chemical heat regulation are to a 



