21 



such activity is patent. This point will be referred to again when 

 describing the tubules. 



Neither in the vesicle of the 9,2 mm embryo nor in that of the 

 13 mm embryo could entodermal cells be demonstrated with terminal 

 bars and ciliated borders as described for occasional cells by Branca. 



Mucinous Masses 



Fat Vacuoles 



Cell Inclusions 



Entoderm 



Blood Vessel 



Fig. 5. 



Fig. 6. 



Fig. 5. Photomicrograph of portion of wall of younger vesicle (of 9.2 mm embryo) 

 showing the character of the entodermal cells, the mesenchyme and the mesothelium. 

 In the lower portion of the section the mucinous masses are especially conspicuous. 

 Magnified 320 diam. Reduced Va in reproduction. Made by Dr. Leopold Jaches. 



Fig. 6. Semidiagrammatic representation (camera lucida outlines) of a portion of 

 the wall of the younger vesicle, showing especially the character of the entodermal cells, 

 with fat vacuoles, mucinous masses and granular and bacillary inclusions. X ''^^'^• 

 Reduced V.i ^^ reproduction. 



The Mesenchyme. 

 The mesenchyme corresponds most closely to the embryonic type 

 though more compact and fibrillar. It consists of stellate and spindle- 

 shaped cells, containing elongated nuclei with one or several nucleoli, 

 and a reticulum with karyosomes (4, 5 and 6). For the most part, 

 however, cell outlines could not be discerned, the whole forming a 

 rather compact syncytium (Figs. 4 and 5). The mesenchyme contains 



