DEVELOPMENT OF THE HYPOPHYSIS 423 
place of attachment of the hypophyseal stalk near the anterior 
end. In a 90 mm. Mustelus this place of attachment can be 
recognized by the very thin floor, and in the adult, by the open- 
ing into the subdural space (Haller ’96, figs. 12 and 40). 
The cavity in the hypophysis of elasmobranchs has been vari- 
ously described as barely distinguishable, slit-like and large. It 
is large in some adult specimens of Acanthias. In the anterior 
lobe there is a distinct increase in the size of the cavity during 
its development. Table 2 will show the actual increase in the 
depth of the cavity. ‘The measurements here given were taken 
in the caudal part of the anterior extremity of the anterior lobe. 
TABLE 2 
Showing depth of the hypophyseal cavity 
LHICE NESS DEPTH THICKNESS OF FLOOR 
SPECIMEN OF en IN OF Rice IN IN MICRA 
Pomp yO. o4 MAM 566 s60 304.0% 31 37 25 
50 mm. 31 13 18 
SOMO ras yeh 2% ote ls 35 12 22 
TPR OL eat SERRE ge ee ee esa 56 90 50 including glandular 
outgrowths 
EC NTTUE Nope Ca en Ro 56 470 480 including glandular 
outgrowths 
The increase in size of the lumen from the pup to the adult 
is thus seen to be considerable. From the table and from com- 
parison with figures 2 to 10 it is seen that the increase in size of 
the lumen is not gradual through all the stages. For example, 
in the 50 mm. embryo the lumen is actually smaller than in a 
34mm.embryo. It is only from the early pup stage on that the 
lumen increases to any considerable degree. The increase in 
size of the lumen of the inferior lobes is even more marked. ‘The 
cavity in the superior lobe is never large. It is very small in a 
48 mm. embryo where the lateral wings are first prominent. 
In a 95 mm. embryo this cavity is small, but is still distinct. 
The lumen of the middle portion of the superior lobe extends 
transversely and forward in the lateral wings of the superior 
JOURNAL OF MORPHOLOGY, VOL. 26, NO. 3 
