GENERAL DIRECTION OF DEVELOPMENT. 



1015 



—-w 



FROM A TO N IS A SERIES OF DIAGRAMMATIC FIGURES SHOWING THE MANNER IN WHICH THE 

 EMBRYO AND ITS ENVELOPES ARE FORMED. 



ttt, Vitelline membrane; e, embryo; pp, pleuro-peritoneal cavity; af, folds of the amnion; a, 

 amnion proper ; ae or ac, cavity containing the liquor amnii ; al, allantois ; a' digestive tabe ; 9 

 or ys, vitellus, or vitellin sac. 



