305 ADOLPH R. RINGOEN 
Undoubtedly the specimens that he examined showed com- 
paratively few buds. I have also frequently found that in em- 
bryos 137mm. in length they are not especially numerous. 
Therefore, since Peterson did not discover the precursors of 
the buds themselves, or the gland rudiments as I have called 
them throughout this paper, he is tempted to theorize with 
reference to the manner in which the number of glands is 
_increased. 
SUMMARY 
1. In the selachians, as represented by Squalus acanthias, 
no specialized cells are set apart in early embryonic life for 
the formation of glands (as described by Miss Ross for Des- 
mognathus, Amblystoma, and pig), but the general epithelium 
is endowed with the capacity of transforming certain groups 
of cells into definite gland rudiments. 
2. The apportioning of the gastric epithelium into glandular 
and non-glandular areas is evident in Acanthias embryos 133 mm. 
in length. At this stage the epithelium is undergoing local 
modification in that small groups of its constituent cells change 
their staining reactions (iron haematoxylin-orange G) as com- 
pared with the adjacent epithelial cells (fig. 2). As soon as an 
epithelial cell is called upon to become a contributory member 
toward the formation of such a group of cells, both its cyto- 
plasm and nucleus decrease in their avidity for the above-men- 
tioned stain. 
3. In addition to this change of staining reactions, there is 
a further change in the morphology of an epithelial nucleus. 
Many a nucleus is seen in the process of changing its shape 
from the typical narrow, elongated type, so characteristic of 
the young epithelial cell, to the plump nucleus of a gland rudi- 
ment cell. 
4. That the potentialities of the epithelial cells are by no 
means the same is particularly evident in the gastric epithelium 
of Acanthias specimens 137 mm. in length. At this stage the 
epithelium is studded at regular intervals with well-defined 
groups of cells. These are no longer to be considered as epi- 
thelial cells, but the rudiments of glands (fig. 3). 
