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in question was slightly collapsed, and inclined towards the left. The 

 sections were cut in a plane lying vertical to the uterus, and hence 

 each primary bud and its two divisions, the secondary buds, are cut 

 transversely. This is jiarticularly true on the right side of the vesicle, 

 because the inclination of the latter makes the right primary bud 

 appear in section as though it occupied a dorsal position. 



In this stage each primary Inid with its two secondary buds is 

 shaped like the letter Y, in which the base represents the proximal 





Fig. 7. Photograph of a lateral section cutting across the tip of embryo 4 of 

 the preceding figure. It shows the embryo beginning to extend out along the inner 

 side of the entoderm as a finger-like process, whose cavity is the amniotic cavity 

 of the embryo (Am). 



Fig. 8. Photograph of a section cutting across the proximal part of the right 

 primary bud of a vesicle in which the secondary buds are well started. 



part of the primary bud and the limbs the secondary buds. Fig. 8 

 is a section through the base of the Y and shows the broad cavity 

 of the primary bud. This is roofed over by the thick ectoderm and 



