506 Edwin G. Kirk. 
In embyro and adult there is found, in passing through this zone 
from left to right, a progressive decrease in mucous chief cells, 
an increase of embryonic gland cells (or, inthe adult, of serous chief 
cells) a gradual lengthening of the whole gland, and a gradual 
relative shortening of the foveola and lengthening of the fundus 
segment. 
Thus at 17-19 em., in the typical fundus area, the bottom of 
the tubule is lined by adelomorphs and parietals, the former 
preponderating. The former do not tinge with muchematin, up 
to the time of their final conversion into zymogen cells, for such 
will soon be their fate. In other words, those cells destined to 
become the serous chief cells, do not pass through a mucous stage, 
but pass directly from the embryonic form to the complete zymo- . 
genic cell. Up to 19 em., neutral gentian, aside from tinting the 
cytoplasm of all the cells a rather faint, diffuse violet or blue, 
stains no granules, except the moderately course ones of the pari- 
etal cells. At 19 cm. granules of a new type appear in the distal 
zone of those cells of the fundic segment of the fundic glands, 
which have hitherto preserved the embryonic type. These 
granules stain, from the first,.a dense blue. At the time of their 
appearance they are slightly larger than the parietal cell granules. 
They do not appear simultaneously in all the adelomorphs, but 
at first in scattered ones, spreading rapidly to the other cells of 
this type, so that, at 25 em. no embryonic gland cells remain in 
the fundus, all having differentiated into serous chief or zymo- 
genic cells. The granules increase rapidly in size, so that they 
are soon much larger than those of the parietals (fig. 22). In 
some cells, from the first, they are not limited to the distal zone, 
but occur throughout that part of the cytoplasm distal to the 
nucleus. The cytodifferentiation of the fundic glands seems now 
complete. | 
The remaining changes are merely such growth processes and 
shifts in the relative size and position of parts, as are necessary to 
bring about the definitive form and positions. As these undoubt- 
edly display much generic, or even specific variation, they can 
have no general developmental significance, such as possessed by 
the details of cytodifferentiation, and will, therefore be described 
but briefly. 
