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HKLKN DEAN KING. 



all of the pigment in the mid-dorsal wall of the archenteron is 

 found to be massed in the outer edges of a very few cells which 

 are entirely cut off from the other cells of the archenteric wall 

 and are attached to the lower surface of the notochord (Fig. 9). 

 These few cells are undoubtedly comparable to the layer of 

 chorda-en doderm found in the mid-dorsal wall of the archenteron 



Fu;s. 8-12. Serial sections from the posterior to the middle region of an embryo 

 of Rana palnstris in which the medullary folds are closing. 



in the toad embryo, and, therefore, the same term may fitly be 

 applied to them. More anteriorly (Fig. 10) there is a noticeable 

 upward bend in the mid-dorsal wall of the archenteron, and it 

 appears as if the notochord with the chorda-endoderm cells is 

 either pulling in or being pushed in from bordering the archen- 

 teric cavity, while the cells of the dorsal wall of the archenteron 



