Reprinted from JOURNAL OF MORPHOLOGY, VOL. 24, No. 4 

 December, 1913 



POLYEMBRYONIC DEVELOPMENT IN TATUSIA 

 NOVEMCINCTA. 1 



J. T. PATTERSON 



THIRTY-FIVE TEXT FIGURES AND ELEVEN PLATES 



CONTENTS 



Introduction 560 



Methods 561 



1. Technique 561 



2. Method of securing early stages 561 



Notes on breeding habits 563 



1. General statement 563 



2. Available material 566 



Development of the blastocyst 569 



1. The monodermic blastocyst 569 



2. The didermic stage 574 



Attachment of the blastocyst 585 



Formation of the ectodermic vesicle 587 



Origin of the extraembryonic mesoderm or mesothelium 593 



Comparison with other forms 595 



Origin of the primary buds 598 



Origin of the secondary buds 603 



Extension of the secondary buds and organization of the embryos 610 



Implantation of ovum and placentation 617 



General discussion 625 



1. Theories of polyembryony 625 



a. Theory of polyovular follicles 625 



b. Theory of blastotomy 629 



c. Theory of budding , 631 



2. Origin of polyembryony in Dasypodidae 636 



3. Polyembryony and duplicate twins and double monsters 641 



4. Polyembryony and sex 643 



Summary 645 



Bibliography 648 



1 Contributions from the Zoological Laboratory of the University of Texas. 

 No. 115. 



559 



