THE AXIAL GRADIENTS IN HYDROZOA. 217 



activity, or conditions associated with it, which play the chief 

 part in modifying the primary susceptibility relations. 



On the basis of studies of oxygen consumption and suscepti- 

 bility in protozoa, E. J. Lund ('i8a, b, c) has criticized the con- 

 clusion that susceptibility to cyanide is a measure of rate of oxi- 

 dation or of metabolism. He has found, first, that Paramecium 

 in cyanide shows no decrease in oxygen consumption until cytol- 

 ysis or disintegration occurs, and second, that in starving Para- 

 mecia oxygen consumption decreases, while susceptibility in- 

 creases. 



In the absence of any attempt to account for the fact that his 

 results apparently disagree completely with current theories of 

 cyanide action, and of convincing evidence that his experiments 

 are controlled with sufficient care, his negative results require 

 further confirmation. But, even assuming that his experimen- 

 tal data are correct as they stand, he has apparently failed to 

 recognize an essential point, viz., that susceptibility as measured 

 by the progress of death and disintegration concerns primaiily the 

 ectoplasm (Child, '146) or the body-surface and body-wall (Child, 

 '156, p. 75). Statements to this effect have been made repeatedly 

 in the work on susceptibility. 1 It is highly probable that in 

 Paramecium the oxidation in the thin layer of ectoplasm is only 

 a very small fraction of the total oxidation, and that, therefore, 

 the decrease in oxygen consumption resulting from the action of 

 cyanide on the ectoplasm is not sufficient to appear w r ith cer- 

 tainty in the total oxygen consumption, w T ith the small amount of 

 material used in his experiments. As soon as the ectoplasm be- 

 gins to disintegrate and the entoplasm is directly exposed to the 

 action of the cyanide, Lund finds a very marked decrease in oxy- 

 gen consumption, i. e., KNC does decrease oxidation at least in 

 the entoplasm in his experiments. The susceptibility method, 

 on the other hand, shows only the conditions in the ectoplasm. 

 In short, Lund's data concerning the effect of cyanide on oxygen 

 consumption in Paramecium are negative and inconclusive, ex- 

 cept as regards the entoplasm, where they are positive and in 

 agreement with current theory. They do not, therefore, justify 



1 Lund's attention was called to this point in personal correspondence soon after 

 the preliminary report of his work appeared (Lund 'i8a). 



