4 H. E. JORDAN 



where the epithelium consists of more than four layers, the one 

 next the basal cuboidal layer is generally composed of more 

 flattened cells. The basal layer seems to rest directly upon the 

 adjacent connective tissue, without the intervention of a definite 

 basement membrane. After picric-acid-fuchsin counterstain, 

 however, a narrow subepithelial layer of the connective tissue 

 stains more deeply red. 



None of the cells contains mitotic figures. An occasional cell 

 of the superficial layer contains two or even four nuclei or a 

 nucleus in process of fission. The nuclei of the cells of the basal 

 layer are of spheroidal shape and contain a clear, lightly staining 

 nucleoplasm and a distinct granular reticulum. These cells are 

 completely filled with a slightly basophilic cytoplasm. The 

 nuclei of the several outer layers are irregular in shape and they 

 have a homogeneous, cloudy, more deep-staining character, and 

 the nuclear wall is generally wrinkled. The cytoplasm of the 

 cells of the intermediate layers is aggregated next the cell wall so 

 that the cell appears hollow. This condition is probably a fix- 

 ation artifact. The nucleus almost invariably lies next the 

 outer wall, as if moved by currents passing toward the surface 

 of the ectoderm. The cells of the outermost layer are again 

 completely filled with an acidophilic cytoplasm. The latter is 

 keratized to an extent w 7 hich could resist the action of the fixation 

 currents that caused the peripheral shrinkage and central excava- 

 tion of the cells of the intermediate layers. 



YOLK-STALK 



The yolk-stalk remnant of one of the two practically full-term 

 specimens of the pig's cord, and of four of the specimens of human 

 cord used for comparative study, is a double structure. In the 

 specimen of the pig's cord the two portions are of nearly equal 

 size (fig. 3). They are approximately circular in outline and 

 perfectly solid. The cells of the peripheral layer are squamous 

 or very low cuboidal. The more central cells are polyhedral «r 

 spheroidal. The cells next the outermost layer are generally 

 flattened and appear , fusiform in longitudinal section. About 



