-l.l vi. tfBMBR \M - OF Kl.l i ILE8 1ND BIRDS, 



209 



cover.- tin- unit rii.r part of tin- In ad like a thin traii-Man-m veil, .-.ml 



is therefore Calli d tilt' cephalic ^heatll. 



In like manner, hut at a somewhat later stage, there arise at the 



tail MM! ami at both sides of the emhryo the post //,// and lateral 



v of the amnion. The posterior foldiR still v-ry iiu-onsiticuouseven 



at tl:o tin).- \\lirii tho head is covered with the veil-like 



(Plate 1., tig. 11 hnj). It tMdar^es slowly, and under the name of 



caudal slu-ath ooven >ver the posterior end of the body (fig. 126 < 



The lateral fol<f. i>/ th>> nmnion are elevated externally to the lateral 

 marginal grooves (tig. 127 out}, and project in the opposite direction 

 from those lateral folds by the bending in of which the lateral and 

 ventral walls of the embryo are produced. Jly thifl means the rim 



14 



