ORIGIN OF THE DEFINITIVE SEX-CELLS IN THE 



FEMALE CHICK AND THEIR RELATION TO 



THE PRIMORDIAL GERM-CELLS 



CHARLES H. SWIFT 



From the Hull Laboratory of Anatomy, University of Chicago 



EIGHT FIGURES 



CONTENTS 



Intti'oduction and review of the literature 441 



Material and methods 446 



Origin and migration of the primordial germ-cells 449 



Later history of the primordial germ-cells 450 



L Primordial germ-cells and the indifferent gonad 450 



2. Primordial germ-cells, the germinal epithelium and medullary cords 



of the embryonic ovary 457 



Cortical cords and origin of the definitive sex-cells 462 



Summary and conclusions 468 



Bibliography 469 



INTRODUCTION AND REVIEW OF LITERATURE 



The question as to the origin of the definitive ova has for a 

 long time been of interest to the biologist. Apparently definitely 

 settled, it has again sprung into prominence owing to the dis- 

 coveries made in regard to the primordial germ-cells — the so- 

 called gonocytes or primordial gonocytes of the French authors, 

 or ureier or urgeschlechtszellen of the German writers. 



Briefly stated, the definitive sex-cells are either lineal descend- 

 ants of the primordial germ-cells or they are developed from 

 peritoneal cells in the differentiated region called the germinal 

 epithelium. 



Waldeyer (70) may be called the first investigator who really 

 attacked the problem. In his work ''Eierstock und Ei" he 

 advanced the opinion that the definitive ova arose from the 

 ureier. These ureier were the larger clear cells, which he ob- 



441 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 18, NO. 3 



