16 LIBBIE H. HYMAN AND ALBERT E. GALIGHER 



SUMMARY 



By means of the susceptibility and electrical methods, evi- 

 dence has been accumulated which clearly indicates the existence 

 of a double metabolic gradient in the oligochaete and polychaete 

 annelids. According to this evidence, the anterior and posterior 

 ends possess the highest metabolic rate, and from these ends the 

 rate decreases toward the middle regions; in the majority of forms 

 the posterior end has a higher metabolic rate than the anterior 

 end. 



In this paper are presented direct determinations of the rate 

 of oxygen consumption per unit weight of pieces from anterior, 

 middle, and posterior regions of the oligochaete Lumbriculus 

 inconstans and the polychaetes Nereis virens and Nereis vexillosa. 

 The results of these determinations are that the posterior pieces 

 of these species consume the most oxygen per unit weight per 

 unit time, the anterior pieces less, and the middle pieces least. 



The results therefore confirm the conclusions drawn by the 

 other methods and establish beyond reasonable doubt the exist- 

 ence of a metabolic gradient in these forms. 



LITERATURE CITED 



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CwiKLiTZER R. 1905 Zur Regeneration des Vorderendes von Ophyotrocha 

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Hyman, L. H. 1916 An analysis of the process of regeneration in certain micro- 

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1918 Suggestions regarding the cause of bioelectric phenomena. 

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1919 On the action of certain substances on oxygen consumption. II. 

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RoBBiNs, H. L., AND Child, C. M. 1920 Carbon dioxide production in relation 

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