CONTENTS OF VOL. XXI. 



ARTICLE I. 

 The ^Morphology of the Pelycosaurian Genus Dimetrodon. By E. C. Case. 5 



ARTICLE II. 



On the (jonstruction of Isobarie Charts for High Levels in the Earth's Atmosphere 



and their Dynamic Significance. By J. W. Sandstrom. 31 



ARTICLE III. 



Chromosomes in the Spermatogenesis of the Hemiptera Heterojitera. By Tiio.m.vs H. 



Montgomery, Jr. 97 



ARTICLE IV. 

 A Study of the Brains of Six Eminent Scientists and Scholars Ijelonging to the Ameri- 

 can Anthropometric Society together with a Description of the Skull of Professor 

 E. D. Cope. By Edw. Anthony Spitzka. 175 



ARTICLE V. 

 A Search for Fluctuations in the Sun's Thermal Radiation through their Influence on 



Terrestrial Temperature. 309 



