CONTENTS 



NO. 1 JULY 



E. J. Lund. The relations of Bursaria to food. II. Digestion and resorption in the 

 food vacuole, and further analysis of the process of extrusion. Eight figures and two 

 plates .' 1 



^Charles W. Metz. Chromosome studies in the Diptera. I. A preliminary survey of 

 five different types of chromosome groups in the genus Drosophila. Diagram and 

 twenty-six figures (plate) 45 



C. M. Child. Studies on the dynamics of morphogenesis and inheritance in experi- 

 mental reproduction. VIII. Dynamic factors in head-determination in Planaria. 

 Two figures 61 



T. H. Morgan. Two sex-linked lethal factors in Drosophila and their influence on the 



sex-ratio. Seven figures 81 



Jacques Loeb. Cluster formation of spermatozoa caused by specific substances from 

 eggs 123 



Roscoe R. Hyde. Fertility and sterility in Drosophila ampelophila. I. Sterility in 

 Drosophila with especial reference to a defect in the female and its behavior in 

 heredity 141 



NO. 2 AUGUST 



Roscoe R. Hyde. Fertility and sterility in Drosophila ampelophila. II. Fertility in 



Drosophila and its behavior in hereditj'. Nine diagrams 173 



Bradley M. Patten. A quantitative determination of the orienting reaction of the 



blowfly larva (Calliphora erythrocephala Meigen). Twenty-four figures 213 



w 



S. J. Holmes. The behavior of epidermis of amphibians when cultivated outside the 

 body. Seven figures 281 



Waldo Shumway. The effect of thyroid on the division rate of Paramaecium. Three 



diagrams 297 



iii 



