CONTENTS 



NO. 1 JULY 



Calvin B. Bridges. A linkage in Drosophila 1 



Jacques Loeb and Hardolph Wasteneys. The relative efficiency of various parts of 



the spectrum for the heliotropic reactions of animals and plants 23 



Leslie B. Arey. The orientation of Amphioxus during locomotion 37 



Maynie R. Curtis and Raymond Pearl. Studies on the physiology of reproduction in 



the domestic fowl. X. Further data on somatic and genetic sterility 45 



Edwin Carleton MacDowell. Bristle inheritance in Drosophila. I. Extra bristles. 



Six figures 61 



NO. 2 AUGUST 



CM. Jackson. Changes in the relative weights of the various parts, systems and organs 

 of young albino rats held at constant body-weight by underfeeding for various periods. 

 Four figures 99 



K. S. Lashley. Inheritance in the asexual reproduction of Hydra. Ten figures 157 



Robert H. Hutchison. The effects of certain salts, and of adaption to high tempera- 

 tures, on the heat resistance of Paramecium caudatum. One figure 211 



Gary N. Calkins. Didinium nasutum. I. The life history. Twelve figures (one 



plate) 225 



NO. 3 OCTOBER 



Morris M. Wells. The reactions and resistance of fishes in their natural environment 

 to salts. Three figures 243 



T. H. Morgan. The predetermination of sex in phylloxerans and aphids. Five text 



figures and two plates 285 



Charles Packard. The effects of the beta and gamma rays of radium on protoplasm. 



Twenty-five figures (three plates) 323 



Theophilus S. Painter. The effect of carbon dioxide on the eggs of Ascaris. Fifteen 



text figures and three plates 355 



iii 



