420 E. A. BAUMGARTNER 
on the development of the skull, made use of such a figure to 
show the interrelation of development of the brain and skull. 
He made an outline drawing of the skull and brain of an embryo, 
choosing an arbitrary magnification. He then made drawings 
of different sized embryos of such a magnification that points, 
corresponding to two arbitrarily chosen in the first drawing, 
would coincide. In figure 27 of this paper, the same scheme was 
adopted. The magnification of the first drawing was such as to 
avoid as much as possible the confusion of lines. The points 
chosen were the extreme anterior end of the notochord and the 
axis of the notochord at the level of the first spino-occipital nerve. 
All the other drawings were then made so that these two points— 
the extreme anterior end of the notochord and the axis of the 
notochord at the level of the first spino-occipital nerve—should 
coincide with those of the first drawing. The outlines of the 
hypophysis were then drawn, using a line between the two points 
as a base. 
The objections to such a drawing are readily apparent. There 
are, of course, individual variations in the embryos. Also, 
these points are probably continually changing during develop- 
ment. For a comparative study, however, the variations can 
be no great objection and the points chosen are probably as relia- 
ble as any. A series of embryos from 11.5 mm. in length to 
the pup were drawn in this manner (fig. 27). One can see at a 
glance in all these stages the relative position of the hypophysis 
with reference to the anterior end of the notochord. Also, 
as was pointed out in the description of the different embryos, 
what is first the dorsal wall becomes in later stages the ventral, 
while the ventral or anterior becomes dorsal. The early superior 
end of the evagination shifts more and more caudalward with 
reference to the rest of the hypophysis, until, in the pup, the 
superior lobe, which develops from the superior dorsal end, is 
caudal in position. The inferior lobes, which develop from the 
sides of the superior end and are on the same horizontal plane 
as the superior position, take a position ventral to the superior 
lobe in the late embryo and adult. The furrows separating these 
inferior lobes, described as appearing in the 20 to 22 mm. embryos 
