CONTENTS 



Krafka, Joseph, Jr. The effect of temperature upon facet number 



in the bar-eyed mutant of Drosophila. Part II 433 



Krapka, Joseph, Jr. The effect of temperature upon facet number 



in the bar-eyed mutant of Drosophila. Part III 445 



Northrop, John H. The influence of hydrogen ion concentration 



on the inactivation of pepsin solutions 465 



Northrop, John H. The effect of the concentration of enzyme on 

 the rate of digestion of proteins by pepsin 471 



Hecht, Selig. The dark adaptation of the human eye 499 



Bailey, I. W. The significance of the cambium in the study of cer- 

 tain physiological problems. Plate 1 519 



Raber, Oran L. a quantitative study of the effect of anions on 



the permeability of plant cells 535 



Raber, Oran L. The antagonistic action of anions 541 



Reed, H. S. The nature of the growth rate . . . .• 545 



Loeb, Jacques. On the cause of the influence of ions on the rate 

 of diffusion of water through collodion membranes. II 563 



Loeb, Jacques. The reversal of the sign of the charge of mem- 

 branes by hydrogen ions 577 



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