CONTENTS. 



PAGE. 



Introduction 391 



History of the Mateer ovum 391 



Serial description of sections 392 



Chorion . 400 



Embryo : 



Embryonic plate 402 



Amnion 403 



Yolk-sac.... . 404 



Angiogenesis . 405 



Comparison with other young human embryos 408 



Probable age of the Mateer embryo ... 416 



Twin embryo .421 



Bibliography . 423 



Description of plates . . . 424 



390 



