IV CONTENTS 



NO. 4 NOVEMBER 



Ruth J. Stocking. Variation and inheritance in abnormalities occurring after conjuga- 

 tion in Paramecium caudatum. Twenty figures 387 



Austin Ralph Middleton. Heritable variations and the results of selections in the fis- 

 sion rate of Stylonychia pustulata. Seventeen figures 451 



Charles Zelany and C. T. Sen ay. Variation in head length of spermatozoa in seven 

 additonal species of insects. Eight figures 505 



Charles Zblany and W. E. Mattoon. The effect of selection upon the 'bar eye' mutant 



of Drosophila. Five figures 515 



Mary B. Stark. The occurrence of lethal factors in inbred and wild stocks of Drosophila. 

 Two diagrams 531 



Jacques Loeb and Mary Mitchell Chamberlain. An attempt at a physico-chemical 



explanation of certain groups of fluctuating variation 550 



