/,/ ^/'rrf rr.sc„t,^^f^ 



ttlIK 



itmb.d. 



I'"iii. 1078.— Diagrams illustrating the development of the foetal membranes of a Bird. A, eail\- 

 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?r. the same growing round the embryo and yolk- 

 an. anus ; hr. brain ; c(jel. coelome ; cieV. extra-em- 

 mth. mouth ; nch. notochord ; .?/<. cd. spinal ciad ; 

 ; vt. in. vitelline membrane ; yk. yolk-sac. 



E E 2* 



a red line ; the mesoderm is grey. all. allantoi; 

 sac ; am. amnion ; am.f., am.J'. amniotic fold ; 

 bryonic cielome ; ht. heart ; ms.ent. mesenteron : 

 ■rr. m. serous membrane ; itmb. d. umbilical duct 



VOL. II 



