authok's abstract of this paper issued 

 by the bibliographic service, january 5 



THE FOR]MATION AND STRUCTURE OF THE ZONA 



PELLUCIDA IN THE OVARIAN EGGS OF 



TURTLES 



ALICE THING 



Anatomical L epartnient , Western Reserve University, Cleveland, Ohio 



TWELVE FIGURES 



CONTENTS 



Introduction 237 



Historical sketch 238 



Material and methods (including possible sources of error) 242 



Observations 244 



A. Epithelium 244 



B. Zona pellucida 246 



a. Stage 1 246 



b. Stage 2 248 



c. Stage 3 250 



Summary 251 



Bibliography. 253 



INTRODUCTION 



In the active research upon eggs of all groups of animals, which 

 has been in progress for nearly fifty years, the zona pellucida, a 

 cuticular membrane, formed around the egg in the course of 

 growth at some stage preceding maturation, has not failed to be 

 an object of interest to investigators and to share with other 

 portions of the egg the most painstaking examination. Accord- 

 ing to Waldeyer ('01, '02, '03, p. 287) there occurs at least one 

 membrane in all vertebrate eggs whereas among invertebrates 

 some eggs remain naked. The majority of vertebrate eggs which 

 have been subjected to careful study show this membrane to be 

 the zona pellucida. It consists typically of two concentric 

 layers, one of Avhich exhibiting characteristic radiating striations 

 perpendicular to the egg surface is termed the zona radiata. 



237 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 2 

 MARCH, 1918 



