On the Histogenesis of Gastric Glands. aay 
residual adelomorphs of the deepest part of the fundic tubules 
differentiate at 19-20 cm. into zymogenic or serous chief cells, 
and then multiply mitotically. 
Thus the parietals are the first of the adult cell types to appear. 
Since the completion of this work, Dr. Bensley has pointed out 
that we have here a very remarkable and extreme instance of 
the throwing back of a coenogenetic character (parietals are not 
definitely identifiable in lower vertebrates) into the earliest 
ontogenetic stage,—a process called by Cope and Hyatt ‘‘accel- 
eration.” 
Phylogenetically, zymogen cells (wde Amphibia), and espe- 
cially mucous cells, are much more primitive, yet they here 
appear in ontogeny later than the parietals. Dr. Bensley has 
suggested that the early appearance of the intracellular ductules 
perhaps points to a functional explanation of this otherwise puz- 
zling ontogenetic anticipation. 
Taken per se, the facts of cytodifferentiation, as recounted 
above, seem to throw no definite light on the problem of cell 
specificity. But studied in conjunction with Harvey’s findings 
(07) they point, I believe, very definitely to certain conclusions. 
The cytodifferentiation proceeds, as if the cells all started 
with the same potentialities or character complexes. These 
might be represented by a, b, and c. In some cells those meta- 
bolic character complexes represented by a become, as develop- 
ment proceeds, dominant, while 6 and c are dormant. In other 
cells, character complex b may dominate, and so on. But the 
dormant character may, under experimentally (Harvey) or pathol- 
logically (Cade, ete., cited by Harvey) altered conditions, become 
the dominant ones. 
The results of the present work seem to indicate that this lat- 
ter process does not occur in the normal course of histogenesis. 
The embryonic cells differentiate directly into the definitive types 
which then give rise, by division, to cell generations of the same 
specialized type. Thus, if the zymogenic characters have become 
dominant in a given cell, during the cytodifferentiation, then 
the off-spring of this cell are al! zymogenic, but, nevertheless, 
the dormant parietal and mucus characters are transmitted to 
