NERVE ENDORGANS IN THE EAR 295 
The 15 sections cut frontally through head and body. The 
membranous labyrinth runs through 102 sections and hence 
has an antero-posterior diameter of 1.53 mm. 
The utriculus and the sacculus communicate by a narrow 
foramen, the canalis utriculo-saccularis; the lateral semicircular 
canal is now an independent structure. Each nerve endorgan is 
well developed. The crista anterior is mound-shaped; the crista 
lateralis is a thick cell mass which appears as a crescent in the 
sections. Both structures still maintain their connection with the 
erista utriculi. 
The tall epithelium of the utricular froor, which diminishes in 
thickness as it passes upward, doubtless represents the first 
anlage of the macula neglecta Retzii. It is continuous with the 
macula partis inferioris through the still cylindrical epithelium 
of the canalis utriculo-saccularis. The macula partis inferior 
consists in this stage of an extended zone of neuroepithelium on 
the medial wall of the pars inferior and already there is to be seen 
on its margin several minimal though unmistakable points devoid 
of nuclei. The fine nerve-fiber bundles that arise from the gan- 
glion acusticum show excellent mitotic figures where the fibers 
enter the macula. The low cylindrical epithelium of the ductus 
endolymphaticus is continuous with the tall neuroepithelium of 
the medial wall of the sacculus. 
Stage 4 (fig. 4). The embryo, which is made up of 23 coils, 
has the appearance of a fully developed individual. Its peculiar 
dermal spots are prominently displayed over the entire body. 
Fixation: formol. Stain: Alcoholic borax carmine. Sections: 
15 » in thickness, cut frontally through the head. 
The nerve endorgans are nearly all differentiated and on each 
the marginal zone free of nuclei may be recognized. The 
cristae anterior and posterior are separated from the macula 
utriculi by a low epithelium. 
It is worthy of notice that the thick epithelium of the utricular 
wall shows clearly a border without nuclei and that it is differ- 
entiated from the epithelium of the canal by its greater thickness. 
It soon becomes thinner as it passes gradually over into the un- 
differentiated epithelium lining the vesicle. This thickening just 
