AUTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 2 



THE DEVELOPMENT OF ASPLANCHNA EBBESBORNII 

 (ROTIFER) 



GEORCxE W. TANNREU.THER 



Zoological Laboratory, University of Missouri 



TWENTY-ONE TEXT FIGURES AND SEVEN PLATES 



CONTENTS 



Introduction 389 



Natural history 391 



Material and methods 394 



Origin and formation of ova 394 



1 . Parthenogenetic 394 



2. Sexual 395 



Cleavage 395 



1 . Designation of cleavage cells 395 



2. Type or nature of cleavage 396 



3. Gastrulation 400 



Segregation of germ layers 401 



1. Ectoderm 401 



2. Mesoderm 402 



3. Entoderm 404 



Formation of trochal region 406 



Digestive system 407 



Reproductive system 410 



Excretory sj'stem 411 



Nervous system 414 



Position of rotifers in the animal kingdom 415 



Summary 419 



INTRODUCTION 



The size of the adult rotifer, in many instances, has made the 

 study of development a difficult problem. A great descriptive 

 mass of literature has grown up around this group of animals, 

 but with the exception of a very few detailed accounts of their 

 structure, the writers have contented themselves with the 

 description of the external form. 



389 ■ 



JOURNAL OK .M0RPH()1.0t,Y, VOL 33, XO. 2 



