Fig 224.— Development of the chick. 



A, part of the ovary sbowin. ova in ^ffere.t sta^^^^^^^ 

 shell removed, showing ''yok suspended by cords ot wnite. ^gu.al-fold stage and extension of 



C, early cleavage of the blastodisc. -D, epg °Pf.^?%\°^fj.°Xtion is becoming established as the blasto- 

 blastoderm over yolk. E and F, stages during whchtbec^^^^^ outgrowth at the posterior 



derm extends further over the yolk.. The allantois appears as a Mada^^ g ^^^^^^^^^^ by the 



end of the embryo in F. G stage in which ^be allantois has enl^^^^^ y growing embryo, 



yolk sac has become reduced by the Progressive ubh^ation of ,^ nutrient ma^^^^^^^^ ^^^ 



In F and G the amnion is shown closely ^^J^^"^"'^"^^ the embryo. « s ^^^^^^ hatching 



/. front view of head showing eyes, nasal openings, mouth, and ears, j, d, Bi,d.s 

 showing yolk stalk and remains of yolk. (Redrawn from Duval.) 



428 



