DEVELOPMENT OF THE HYPOPHYSIS 425 
HISTOLOGY AND HISTOGENESIS 
1. Histology of the adult hypophysis 
a. Anterior lobe. The deep median sulcus in the floor of the 
anterior lobe has been noted above. It has been observed by 
Sterzi and others in various selachians. The furrows noted in 
the floor of the anterior extremity in the pup are evidence of 
the beginning formation of tubules. Haller observed the tub- 
ules on the ventral wall of the anterior part in Mustelus, Gentes 
observed them in Torpedo, and Sterzi in Acanthias. Tilney 
(11) stated that there are many vesicles in the upper and lower 
walls of the juxta-neural (anterior) part in Acanthias. Haller 
figures cyst-like glands in the roof of the anterior lobe of Mustelus. 
Some adult specimens of Acanthias show glandular outgrowths 
in the superior wall of the anterior lobe, especially in the dorso- 
lateral parts of the anterior extremity. As Sterzi (’09) observed, 
glands probably develop from the anterior lobe throughout life 
and, finally, even from the dorso-lateral walls and roof, and 
glands project ventrally from the floor of the anterior lobe. 
A model of some of the latter shows that branches are given 
off at all angles from the first large tubule extending ventrally 
-and that secondary and tertiary outpouchings occur from the 
branches. The tubules anastomose among each other and with 
those from other glands both cranially and caudally, but not across 
the median sulcus with the glands of the other side. The lumina 
may be continuous through the anastomosing tubules. <A cast 
of the lumina shows frequent enlarged cavities from which small 
openings lead to the cyst-like cavities found in some of the 
secondary and tertiary tubules. No such glands were observed 
in any other part of the anterior lobe. If any glands be present 
in the roof of the anterior end they are simple and cystic or 
acinar in character. In some specimens, probably older animals, 
there are large tubular glands in the floor and lateral walls and 
even in the roof of the caudal extremity. The floor of the middle 
part occasionally shows cystic glands. The walls of the tubules 
are two or three cells thick and the columnar cells forming them 
are at right angles to the surface (fig. 28). There is a periph- 
