PLATE 2 



EXPLANATION OF FIGURES 



2 Photomicrograph of the ectodermal covering of the cord in the region, 

 Som., of figure 1. It includes four or five layers of cells and resembles transitional 

 epithelium. The lowermost layer is composed of cuboidal cells; the outermost 

 layer includes dome-shaped, rectangular, and flattened peridermal cells; the 

 intermediate layers include spheroidal and polyhedral cells. X 300. 



3 Photomicrograph of remnant of yolk-stalk (fig. 1, Y.S.). It is double and 

 occluded, and each moiety includes about twelve cells in its diameter. Art., 

 arteriole. X 300. 



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