rpretation-- doubt that, if anything,
is gaining ground.

Section 32. The tympanic bulla of the dog is not indicated in Diagram
9, and it would appear to be a new structure (neomorph), not
represented in the frog.

Section 33. Besides these great differences in form, there are
important differences in the amount and distribution of centres of
ossification of the skull of frog and mammal. There is no
parasphenoid in the mammal*; and, instead, a complete series of
ossifications, the median-, basi-, and pre-sphenoids, and the lateral
ali- and orbito-sphenoids occur. The points can be rendered much
more luminously in a diagram than in the text, and we would counsel
the student to compare this very carefully with that of the Rabbit.

* Faint vestigeal indications occur in the developing skulls of some
insectivora.

Section 34.

-Cranium_

-Nasal_ (paired), -Vomer_ (paired)
-Fronto-Parietal_, Sphenethmoid Bone (median), Eye, Pro-otic Bone,
Otic Cartilage, Ex-occipital (paired)
-Para-sphenoid Bone_

-Upper Jaw_

-Pre-Maxilla_ (paired), -Palatine_ (paired), Pterygoid (paired),
-Squamosal_, Quadrate Cartilage {To 1.}
-Maxilla_
1. Quadrato-Jugal

-Lower Jaw_

Mento-meckelian, -Dentary_, -Articulare- [-Angulo Splenial_]

Section 35. -Points especially- [Additional points] to be noticed are:

(1) The otic capsule (= periotic bone) of the dog ossifies from a
number of centres, one of which is equivalent to the frog's prootic.

(2) The several constituents of the lower jaw are not to be
distinguished in the adult mammal.

(3) The frog has no lachrymal bone.

Section 36. We are now in a position to notice, without any danger of
misconception, what is called the segmental theory of the skull. Older
anatomists, working from adult structure only, conceived the idea that
the brain-case of the mammal represented three inflated vertebrae.
The most anterior had the pre-sphenoid for its body, the
orbito-sphenoids for its neural processes, and the arch was
completed above by the frontals (frontal segment). Similarly, the
basi-sphenoids, ali-sphenoids, and parietals formed a second arch
(parietal segment), and the ex-, basi-, and supra-occipitals a third
(occipital segment). If this were correct, in the frog, which is a more
primitive rendering of the vertebrate plan, we should find the vertebral
characters more distinct. But, as a mat