author's abstract of this paper issued 

 bt the bibliographic service, july 19 



RELATIVE EFFECTIVENESS OF FOOD, OXYGEN, AND 

 OTHER SUBSTANCES IN CAUSING OR PRE- 

 VENTING MALE-PRODUCTION IN 

 HYDATINAi 



A. FRANKLIN SHULL 



Zoological Laboratory, University of Michigan 



CONTENTS 



Introduction 521 



Experiments 522 



Effect of 60 per cent oxygen 522 



Amount of oxygen dissolved from atmosphere and from Euglena 525 



Direct solution of oxygen 526 



Oxygen derived from photosynthesis 529 



Englena versus oxygen and other substances as male-producing or male- 

 repressing agents 532 



Response to oxygen in Nebraska line 538 



Discussion 539 



Summary 543 



Bibliography 544 



INTRODUCTION 



A paper on the effect of oxygen on the hfe cycle of the rotifer 

 Hydatina senta by Shull and Ladoff ('16) left certain matters in 

 doubt. Whereas water saturated with a mixture of air and 

 oxygen which contained 40 per cent of oxygen caused an increase 

 in the ratio of male-producers to female-producers, saturation with 

 a mixture containing 60 per cent of oxygen was attended 

 by practically no results. Two explanations seemed possible. 

 Either different concentrations of oxygen had different effects 

 or oxygen was incapable of increasing male-production when 

 male-production was already high from other causes. The 



^This investigation was aided by a grant from the Bache fund of the National 

 Academy of Sciences, to the trustees of which the author desires to make grate- 

 ful acknowledgment. 



521 



