vl CONTENTS 
PAGE 
CHAPTER IV. FROM LAYING TO THE FORMATION OF 
THE FIRST SOMITE... . i) Gl Rao 
STRUCTURE OF THE UNINCUBATED BLASTODERM. . . . 69 
II.. Tee PRIMITIVE STREAK. 3. 9. (2) 4) 5. 9S ee ee 
Potal Views. ae ae Se We 5 cee ep ee 
Sections — . b - so sB, Sy. Gs 9 ee ee 74 
The Head-process ; «Ue edt ge aa 
Interpretation of the Pr inne Str aE . 6 eke Sees 
III. THe MrsopERM OF THE OpaQuE AREA . ... . . 86 
TV. Tae GerRM-wWabh - . *s 6s iy ow ww oe oe 1 ee 
CHAPTER V. HEAD-FOLD TO TWELVE SOMITES 
(From about the twenty-first to the thirty-third hour of incu- 
bation) er Ee SS ade A. ae ee 
I. ORIGIN OF THE Aire AD-FOLD 9." 2 2» <) » 0» . 9 seme 
II. FoRMATION OF THE FoRE-GUT. . . . ... . . 98 
Ill. OriGciIn oF THE NEURAL TUBE bus eh a a ey Cag 
The Medullary_Plate. . . . . . «1 . . « « 
The Neural Groove and Folds. . . . . . . 97 
Primary Divisions of the Neural Tube... - £05 
Origin of the Primary Divisions of the Embryonic Bram 108 
IV. Tue MESoBLAST . . . «© « w 2 Se Beg 
Primary Structure of ile See Sg a “eS le Ce ie 
The Nephrotome, or Intermediate Cell-mass (Middle 
‘Plate Fe ee eles 
The Lateral Plate. . . oe ee SES 
Development of the Body-c Piva or Chisme « fe oe ie a ID 
Mesoblast of the Head . . . . . . . . . . 42116 
Vascular System .9. : 2. 2 & % .« = «» 4 ~ ig 
Origin ofthe Heart . . . . .... . . «. JY 
The Embryonic Blood-vessels 5. ow « fe ae 
V. DESCRIPTION OF AN EMBRYO WITH 10 Somme » 4 oe alee 
The Nervous System . . . . . . .. . . . 4124 
Alimentary Canal > as Vo Se 8 A 
Vascular System™, > G.8e_« % we elo 
General : : Se bape Se he ogee A Voller 
Zones oj the Blesindoem oes & We 2 eae 
CHAPTER VI. FROM TWELVE TO THIRTY-SIX SOMITES. 
THIRTY-FOUR TO SEVENTY-TWO HOURS . 1380 
I. D&rVELOPMENT OF THE EXTERNAL FORM, AND TURNING OF 
THE EMBRYO . . 2 oe Us OU SO 
Separation of the Embryo on the Blasters . » ay dO 
