FOWL— SECOND AND THIRD DAYS 



533 



It is advisable to make a careful study of the anatomy of an 

 embryo of about the stage shown in Fig. 235 or 236. 1 



Fig. 235. — Third-day Fowl embryo with the vascular area. 



a.e t edge of amnion ; E, eye ; H, heart ; ot, otocyst ; s.a, sero-amniotic connexion ; s.t, sinus 

 terminals ; t.f, tail-fold; r.a, vitelline artery; *, portion of splanchnopleure involuted to form a. 

 recess round the head of the embryo. 



1 It is customary to mount transverse sections with the posterior or tailward surface 

 of the section next the slide : consequently the figures represent the sections as seen 

 from in front and the side of each figure towards the right-hand side of the page 

 corresponds to the left-hand side of the embryo. 



