422 E. A. BAUMGARTNER 
on the ventral (anterior) side of the hypophysis, are later (50 
mm. embryos) on the dorsal side. The anterior lobe, first 
directed almost vertically, grows ventrally and later extends 
more and more anteriorly until it is directed horizontally (ecranio- 
caudally). 
The comparative growth of the different portions is also made 
clear. The anterior lobe comprises all of the original outpouch- 
ing and also the anterior tongue which evaginates later. The 
increase in length of the anterior lobe, particularly its anterior 
extremity,is marked. The inferior lobes, developing from the 
sides of the posterior portion of the early evagination, become 
continuous across the posterior side (34 mm. embryos) and finally 
constrict entirely except for a short duct connected with the 
anterior lobe. The inferior lobes increase greatly in size, but, 
in the adult, are largest transversely. The superior lobe, de- 
veloped from the superior dorsal part, spreads far out trans- 
versely and later enlarges in its dorso-ventral axis. 
The posterior extremity of the anterior lobe is then developed 
from the first outpouching. <A little later (21 mm.) the part 
anterior or ventral to the original outgrowth evaginates, forming 
largely the middle narrower portion of the anterior lobe. The 
anterior extremity of the anterior lobe develops at the extreme 
anterior (ventral) end of this. The stalk connecting the hypophy- 
sis with the mouth is attached to the middle narrower portion. 
The connection between the inferior lobes develops caudal 
(dorsal) to this but arises from a part which later becomes 
the floor of the posterior extremity of the anterior lobe. From 
this description it is seen that the inferior lobes, developing from 
the posterior end of the hypophyseal anlage, and the superior 
lobe, from its extreme dorsal (anterior) end, are derived from a 
part of the anterior lobe. Such an explanation of the develop- 
ment of the parts is well borne out by a study of the models as 
well as of the various sections of embryos. 
In comparing figures 6, 7 and 8 it is seen that the hypophyseal 
stalk in a 40 mm. embryo is attached nearer the caudal end of 
the hypophysis than it is in younger ones. This does not agree 
with what Haller has described for Mustelus when he found the 
