ORIGIN AND EARLY HISTORY OF THE PRIMORDIAL 

 GERM-CELLS IN THE CHICK 



CHARLES H. SWIFT 



From the Hull Laboratory of Anatomy, University of Chicago 



FIFTEEN FIGURES 



CONTENTS 



Introduction and review of the literature 483 



Material and methods 489 



Origin and history of the primordial germ-cells 491 



1. Structure of the germ-cells 491 



2. Migration of the germ-cells 496 



3. Origin of the germ-cells 510 



Summary and conclusions 514 



Bibliography 515 



INTRODUCTION AND REVIEW OF THE LITERATURE 



There are several theories held as to the origin of primordial 

 germ-cells. The theory that they arise from a differentiated por- 

 tion of the coelomic epithelium over the Wolffian body has pri- 

 ority and should be mentioned first. Waldeyer ('70) was the 

 first to advance this idea as to an origin from a so-called germinal 

 epithelium. His opinion advanced in the work ''Eierstock und 

 Ei," remained unchallenged for a long time. It has had a num- 

 ber of supporters, and e\'en at the present day, the theory that 

 the primordial germ-cells arise in the germinal epithelium, is the 

 only one found in a majority of text-books. That this theoiy 

 should have a long life is only natural. The early investigators 

 did not possess the finished methods or perfected instruments of 

 today and so were placed at a serious disadvantage when working 

 with the younger stages. Also, as we now know, the germ cells 

 in the earlier stages of development, are not grouped, but may 

 be widely scattered, and for this reason, if for no other, they 



483 



