FIG. 1078. Diagrams illustrating the development of the foetal membranes of a Bird. A, early 

 stage in the formation of the amnion, sagittal section ; B, slightly later stage, transverse section ; 

 C, stage with completed amnion and commencing allantois ; D, stage in which the allantois has 

 begun to envelop the embryo and yolk-sac. The ectoderm is represented by a blue, the endoderm by 

 a red line ; the mesoderm is grey. all. atlantois ; all', the same growing round the embryo and yolk- 

 sac ; am. amnion ; am.f., am./', amiiiotic fold ; an. anus ; br. brain ; ecel. coelome ; ccel'. extra-em- 

 bryonic coelome ; lit. heart ; ms.ent. mesenteron ; mth. mouth ; nch. notochord ; p. cd. spinal cord : 

 ar. m. serous membrane ; umb. d. umbilical duct ; vt. m. vitelline membrane ; yk. yolk-sac. 



VOL. II E E 2* 



