ArTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BT THE BIBLIOGRAPHIC SERVICE, DECEMBER 1 



EXPERIMENTAL STUDIES ON THE LIFE-HISTORY 



OF A ROTIFER REPRODUCING PARTHENO- 



GENETICALLY (PROALES DECIPIENS) 



BESSIE XOYES 

 Zoological Laboratory of the Johns Hopkins University 



CONTENTS 



Introduction 225 



The normal life-history and reproduction, with vital statistics 227 



Do males occur? An experimental study 233 



The effect of selection 239 



The effect of alcohol in relation to inheritance 244 



Summary 253 



Literature cited 254 



INTRODUCTION 



Proales decipiens, a small rotifer belonging to the family of 

 Notommatidae, presents unusual opportunities for studies on the 

 life-history of the Rotifera, for work on long-continued partheno- 

 genesis, and particularly for attempts to alter racial charac- 

 teristics by selection or by environmental action. The animal 

 lives in cultures of decaying vegetable material; it thrives in the 

 hay infusions, malted-milk solutions, and the like, commonly 

 employed for cultures of Paramecium. It is extremeh^ hardy, 

 readily lends itself to culture of isolated individuals on hollow- 

 ground slides, and thrives under wide ranges of environment. At 

 laboratory temperature it begins to produce eggs twenty-four 

 to thirty-six hours after hatching. The number is low on the 

 first day, increases gradually until the fifth day, then declines 

 sharply, and egg production ceases on the seventh or eighth day, 

 and the death of the adult follows in one or two days. In a 

 typical life-cycle an egg deposited by the mother hatches in 

 twelve to twenty-four hours; the embryo reaches the egg-laying 

 period in twenty-four to thirty-six hours after hatching and 



225 



