ORIGIN OF THE SEX-CORDS AND DEFINITIVE 

 SPERMATOGONIA IN THE MALE CHICK 



CHARLES H. SWIFT 



From the Hull Laboratory of Anatomy, University of Chicago 



SIX FIGURES 



CONTENTS 



Introduction and review of literature 375 



Materials and method of study 383 



The indifferent gonad 385 



Differentiation of sex and origin of the sexual cords 387 



The evolution of the sexual or seminiferous cords of the embryonic testis... 390 

 The interstitial cells and the mitochondrial crescent of the spermatogoniimi. 403 



Summary 407 



Bibliography 409 



INTRODUCTION AND REVIEW OF LITERATURE 



The year 1870, in which appeared Waldeyer's famous article, 

 Eierstock und Ei, really marks the beginning of modern research 

 relative to the sex glands, their origin and products. 



According to a majority of the investigators who have studied 

 the question since 1870, there are two possible sources of origin 

 of the definitive male cells — either from cells of the germinal 

 epithelium or from primordial germ-cells. 



These terms require some elucidation and wdll be explained 

 before taking up the more important articles which bear on the 

 subject. 



In the early stages of all vertebrate embryos, the epithelium, 

 or mesothelium, lining the coelomic cavity is flat and a single 

 layer of cells in thickness. After the appearance of the Wolffian 

 body the coelomic epithelium on its ventro-medial surface 

 begins to change. The cells begin to elongate and become co- 

 lumnar or cylindrical and they may finally be several layers in 

 thickness. This change is strictly limited; viewed in section 



375 



