j88 LIBBIE H. HYMAN. 



it is about half of that of Planaria but it must be remembered 

 that a considerable portion of the weight of the sponge is due to 

 the lifeless spicules. 



Of the twelve experiments presented in Table I., the rate of 

 oxygen consumption is markedly greater in the apical piece in 

 five cases (Nos. 3, 5, 7, 9, and 12), slightly greater in five cases 

 (Nos. 4, 6, 8, n, and 13) and about equal to that of the basal 

 piece in two cases (Nos. I and 2). In experiments 4 and 6 the 

 difference between the apical and basal pieces is so slight as 

 probably to be of no significance. 



The experiments on carbon dioxide production yield about the 

 same result. In nine cases, the apical pieces produce carbon 

 dioxide at a faster rate than do the basal pieces, in one case 

 (No. 5) the rate is equal and in one case (No. 4) the result is the 

 reverse. The advantage in favor of the apical piece is not very 

 great in Nos. 10 and n. 



These findings are in agreement with the electrical differences 

 previously discovered in this sponge (Hyman and Bellamy, '22). 

 It was found that in the majority of individuals the oscular end 

 is electropositive (internally) to more proximal regions, but that 

 in some individuals this potential difference is absent or may even 

 be reversed. That these electrical differences are correlated 

 with the metabolic differences is a view which I have held for a 

 number of years. It is presumable that those individuals in 

 which electrical or metabolic gradients are lacking are in poor 

 physiological condition. 



Finally attention may be called to the relation between rate 

 of oxygen consumption and size (weight). In general, the greater 

 the weight of the pieces, the lower is the rate of oxygen consump- 

 tion. This inverse relation between size and respiratory rate 

 seems to be general throughout the animal kingdom (cf. Hyman, 



'19). 



5. Summary. In the majority of cases, apical pieces of tin- 

 body of the sponge Grantia consume oxygen and produce carbon 

 dioxide at a higher rate per unit weight than do basal pieces. 

 This result furnishes further evidence in favor of the axial 

 gradient conception. 



