FACTORS AFFECTING MALE-PRODUCTION IN 

 HYDATINAi 



A. FRANKLIN SHULL AND SONIA LADOFF 



Zoological Laboratory, University of Michigan 



ONE FIGURE 



CONTENTS 



Introduction 127 



Experiments on the mechanism of the prevention of male-production 128 



Osmotic pressure 128 



Acidity 130 



Delay or inhibition by manure solution 130 



Experiments designed to increase male-production 132 



Effect of various salts 133 



Factors suggested by Whitney's experiments 137 



Effect of dilute bouillon 139 



Effect of metabolic products of a green alga 140 



Effect of oxygen 143 



Discussion ■ 156 



Summary 160 



Bibliography 161 



INTRODUCTION 



After it had been well established that certain agents reduce 

 the number of male-producing females in the families of the 

 rotifer Hydatina senta, two important related lines of investi- 

 gation were undertaken. One sought to explain how these agents 

 operated to prevent the appearance of male-producers ; the other 

 had for its object the discovery of means of increasing the num- 

 ber of male-producers. The former line of research has proven 

 nearly fruitless; the latter has met with some success. The 

 experiments described in this paper were aimed at the solution 

 of these two sets of problems. 



1 Contributions from the Zoological Laboratory of the University of 

 Michigan. 



127 



