iv CONTENTS 



FiiANCis B. Sumner. Geographic variation and Mendelian inheritance. 



Seven figures 369 



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

 in experimental reproduction. X. Head-frequency in Planaria doroto- 

 cephala in relation to age, nutrition and motor activity 403 



No. 4. MAY 



Edwin Carleton MacDowell. Bristle inheritance in Drosophila. III. 



Correlation. Eight figures 419 



Minna E. Jewell. The effects of hydrogen ion concentration and oxygen 



content of water upon regeneration and metabolism of tadpoles. 



Twenty-four figures 4G1 



