1G3 
ME. W. K. PAEKER OR THE STRUCTURE AND 
part of each eyeball ( e .) is shown. The next section (fig. 8) made through the posterior 
part of the hemispheres shows a flatter and thicker floor, and diminished trabecular 
and upper thickenings; the frontals (f.) nearly cover the top; and the parasphenoid 
(pa.s.) largely underlies the floor. 
Another section (fig. 9) passes exactly through the middle of the posterior sphenoidal 
region, cutting through the optic lobes and infundibulum (C 2, inf.) ; and here we see 
that the “infundibulum” rests upon a cartilaginous floor, the original hypophysial space 
being filled-in by a long commissure. Here also we see an ichthyic condition — namely, 
perfectly continuous cartilage, from base to top, overlain by the bony matter (fp.) of the 
“coronal” synostosis. Here, again, the trabecular thickenings (tr.) are evident; but on 
the whole the cartilage is thin. 
If we look at the sectional view of the Tadpole’s skull (Plate Y. fig. 2), below and 
behind the infundibulum {inf.) the skull floor is imperfect. This is a remnant, partly 
of the original pituitary space, and partly of the fissure between the moieties of the 
investing mass in which the notochord terminated (Plate V. figs. 3 & 4). 
In this stage it has expanded (Plate IX. fig. 10, p.b.c.f.) into the “posterior basicra- 
nial fontanelle” of Eathke ; it is only transitory in the Frog. 
The “ stern” of this barge-shaped skull keeps its “deck” now to the end; it becomes 
extremely wide, having the ear-capsules impacted in its sides. In the sectional view 
(Plate VII. fig. 10) the thin cartilaginous roof, cut through where the supraoccipital region 
passes into the “ pterotic,” is seen to pass directly into the ear-capsule, close above the 
arch of the posterior canal (p.s.c.). The apparent want of continuity in the rest of the 
section arises from the fact that it has been made through the “ fenestra ovalis” ( fs.o .) 
and the “meatus internus” (7 A ). The basitemporal wings of the parasphenoid ( pa.s .) 
underlie most of the width of the broad basicranial floor in which the notochord ( n.c .) 
lies imbedded ; it is here free above, and, below, lies on a cartilaginous commissure. 
Part of the stapedial plate ( st .) has been left to this section, which also shows the 
posterior half of the horizontal canal (. h.s.c .), the vestibule (v.b.), and the huge “medulla 
oblongata ( m.ob ) large as this is, it does not fill the cranial cavity. The two remnants 
of the notochordal fissure are seen from above in Plate IX. fig. 1 more highly magnified 
(30 diam.). The gelatinous remnant of the notochord (n.c.) is seen in the posterior 
space, which is a deep groove ; the anterior space is the triangular “ posterior basicranial 
fontanelle.” 
The changes that have taken place in the sub ocular or palato -quadrate arch are very 
instructive. 
The anterior crus is becoming very long in proportion to the posterior, and the palatine 
portion (pci.) is very nearly constricted off from the pterygoid (p-g.). 
The small knuckle in front of the bend in the palatal has now become a spur (Plate VIII. 
figs. 1 & 2), so that there are now three regions to the palatal, namely the suspensorial 
or “ suprapalatal,” the “ prepalatal,” and the postpalatal (Plate VII. fig. 11, e.pa., prpa ., 
and pt.pa.). 
