AUTHOR S ABSTRACT OF THIS PAPER ISSUKD 

 BY THE BIBLIOGRAPHIC SERVICE OCTOBER 27. 



THE EARLY HISTORY OF THE GERM CELLS IN THE 

 ARMADILLO, TATUSIA NOVEMCINCTA 



AIMEE S. VANNEMAN 

 Contribution from the Zoological Laboratory of the University of Texas, No. 137 



THREE PLATES AND TWO TEXT FIGURES 



CONTENTS 



Introduction 341 



Structure of germ cells 346 



Germ cells in early stages 347 



Migration of germ cells 350 



Discussion 354 



Summary and conclusions. 356 



Bibliography 357 



INTRODUCTION 



In addition to the interest attached to a problem of this sort, 

 there are thi'ee reasons for undertaking the work of the present 

 paper. Fu'st of all, the germ cells of the armadillo are remark- 

 ably conspicuous, even in young stages. Probably no other 

 mammal so far studied for the point in question, offers such pos- 

 sibilities for the solution of a yet unsettled problem. The germ 

 cells of the armadillo, besides being clear-cut are easily trace- 

 able thi'ough the tissues, without the characteristic details found 

 necessary for recognition in forms investigated by other workers. 

 Again, the armadillo presents a problem of unusual interest in 

 being a polyembryonic form. Here, it is a question as to whether 

 or not the germ cells of the embryos of a given blastocyst have 

 a common origin. It is to be noted that no one has ever traced 

 germ cells with certainty to a pre-embryonic stage in a poly- 

 embryonic form. The discovery by Swift ('14, '15), that germ 

 cells in the chick migrate by way of the blood-vascular system, 

 stimulates further investigation as to the path of ixiigration of 



341 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 3 

 NOVEMBER, 1917 



