ORIGIN OF GASTRIC GLANDS OF ACANTHIAS 353 
He believes that the gastric glands appear phylogenetically 
first in the selachians. 
The literature on the glands of the Selachii has been to a 
large extent reviewed by Oppel (’96), but one finds very little 
information relative to the origin of the gastric glands themselves. 
Sullivan (’07), in the course of a study devoted to the diges- 
tive tract of Elasmobranchs, considers primarily the physio- 
logical features of the glands. He makes no comment upon 
the development of the glands. 
Peterson (’09) is, as far as I am able to ascertain, one of the 
few investigators to consider in some detail the development 
of the gastric glands in selachians. In his studies on the 
histogenesis of the glands in a number of these forms he de- 
scribes and figures epithelial outgrowths as the rudiments of 
glands. 
OBSERVATIONS 
In Squalus acanthias, gland development proceeds in a very 
different manner from that commonly described for a number 
of mammals, including man. The conditions in the gastric 
epithelium of embryos 133 mm. in length indicate that in the 
selachians gland formation is not associated with the formation 
of gastric pits, as has been claimed for man. Since Acanthias 
specimens of this length show the first traces of gland dif- 
ferentiation, I begin with this stage and follow out in later stages 
the complete evolution of a gland. 
A. Early changes in the gastric epithelium 
The early stages in the development of gastric glands are 
clearly followed in Squalus acanthias embryos 133 mm. long. 
In fact, the very beginnings of the glands are discernible here 
as differentiating in the gastric epithelium itself. At this par- 
ticular stage the epithelium of the stomach is characterized 
by its great activity in the way of undergoing definite local 
changes throughout its entire extent. Prior to the 133-mm. 
stage there were no apparent variations or irregularities in it; 
