THE DEVELOPMENT OF THE NINE-BANDED ARMA- 

 DILLO FROM THE PRIMITIVE STREAK STAGE TO 

 BIRTH; WITH ESPECIAL REFERENCE TO THE 

 QUESTION OF SPECIFIC POLYEMBRYONY 1 



H. H. NEWMAN AND J. THOMAS PATTERSON 

 From the Zoloogical Laboratory, University of Texas 



FIFTEEN TEXT FIGURES AND NINE PLATES 



CONTENTS 



I. Introduction 360 



A. Review of the literature 360 



B. Material and methods 363 



C. Purpose and scope of the present paper 364 



II. The female genitalia 365 



III. Number, arrangement and sex of embryos 367 



A. Number of embryos 367 



B. Airangement of embryos 368 



C. Sex of embryos 370 



IV. The early embryology 371 



A. The earliest stages of Fernandez 371 



B. The primitive streak stage 374 



C. The five to seven somite stage 380 



V. History of the placenta 384 



VI. History of the amnion 393 



VII. History of the allantois and the umbilicus 39& 



VIII. Pairing of the embryos 397 



IX. Conditions in vesicles containing five foetuses 401 



X. The question of identity of embryos 405 



XI. Specific polyembryony and the determination of sex 406 



XII. Summary of evidence for specific polyembryony 409 



Bibliography 411 



1 Contribution from the Zoological Laboratory of the University of Texas, 

 No. 105. 



JOURNAL OF MORPHOLOGY, VOI . 21, NO. 3. 



473380 



