ORIGIN OF GASTRIC GLANDS OF ACANTHIAS Gt 
kennen gelernt, und sie kénnten also auch spiterhin Driisen- 
knospen entwickeln. Die anderen Zellen der basalen Reihe 
sind vollkommen verschwunden—aufgebraucht.’? He _ states, 
however, that he has no proof for such activity on the part of 
the neck cells. 
_Peterson’s statement, ‘‘bei einem jungen Tiere hat die Schleim- 
haut dasselbe Aussehen wei bei einem alten,’’ is absolutely 
not in accordance with my observations. Figures 2 and 3 
show that there are decided morphological and staining dif- 
ferences, and in these specimens, from which the drawings were 
made, there is only a difference of 4mm. in length. In figure 
2 (embryo 133-mm. long) the epithelium is undergoing definite 
changes, while in figure 3 (137-mm. long) it shows more decided 
changes—the rudiments of glands. 
It is unnecessary to build any elaborate theories with ref- 
erence to the manner in which the number of glands is increased, 
as Peterson has attempted to do. Any attempt with such an 
aim in view is diametrically opposed to what one finds in the 
gastric epithelium of Acanthias specimens 137 mm. in length. 
At this stage the epithelium has been modified at only those 
points where glands are to be established, and, indeed, it is 
surprising with what regularity and precision these changes 
occur. The entire epithelium is literally studded at regular 
intervals with them. Every gland of the adult animal is rep- 
resented at this stage by its own epithelial modification, or 
gland rudiment. In specimens 146mm. long and above this 
length, all the rudiments have given origin to glands, and the 
neck portion of every gland occupies the same relative position 
in the epithelium as did the early gland rudiment. The entire 
process of glandular development takes place in just as orderly 
a manner as does the differentiation and development of any 
other vertebrate organ or structure. 
Peterson’s entire difficulty in failing to be able to account 
for the vast numbers of glands in old specimens is easily 
explained. Although he saw numerous epithelial buds (‘Knos- 
pen’) in young specimens, they were by no means sufficiently 
numerous to account for all the glands in the adult specimen. 
