. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 8G ANATOMY OP VERTEBRATES. trunk by a pair of condyles, fig. 72, e, e, is resumed. The chief steps In the developement of the batrachlan skull will be premised before entering upon the various modifications. In the larva of the frog, fig. 42, the outer layer of the notochordal capsule expands at the fore part of that vertebral basis to enclose the brain, and its appen- dages, the sense-organs. The cartilage therein developed, fig. 68, as the head expands, forms an occipito-petrosal mass, fig. 42, 16, including laterally
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 8G ANATOMY OP VERTEBRATES. trunk by a pair of condyles, fig. 72, e, e, is resumed. The chief steps In the developement of the batrachlan skull will be premised before entering upon the various modifications. In the larva of the frog, fig. 42, the outer layer of the notochordal capsule expands at the fore part of that vertebral basis to enclose the brain, and its appen- dages, the sense-organs. The cartilage therein developed, fig. 68, as the head expands, forms an occipito-petrosal mass, fig. 42, 16, including laterally the ear-cajisules; it bifurcates anteriorly into the ' sphenoidal arches,' wliich reunite in front of an oblong hypophysial space to form a broad prefronto-vomerine mass. The occipito-petrosal cartilage sends out on each side a tliick ' masto- tympanic' process, which bifurcates; the division directed for- ward and inward fig. 42, 26, is the ' pterygoid;' that passing forward and downward is the ' hyjDotympanic' To the back part is attached the hyoid cartilage, ib. 4o: to the end is attached the 'mandibular' cartilage, ib. so, fig. 69a, d, also called 'Meckel's process.' The subsequent ossification begins partly iii the carti- lage, partly in the piersistent notochordal membrane: the first may be called ' chondrogenous,' the second ' sclerogenous ' bones : some are disjwsed to regard the first only as ' endoskeletal,' the latter as ' exoskeletal.' To the first category belong the neurapophyses of the occijuit, exoccipitals, figs. 43 and 68, 2 ; each of which developes a ' zygapo- physis ' or condyle, fig. 73, e, for tlie atlas, fig, 43, a : any petrosal ossification upon the ear-capsule is a growth from the cxoccipital and from the alisplie- nuid, ib. 6 : the expanded disc of the ' columella' or ' stapes' is a distinct ossicle, between 2 and 25, fig. 43 ; as is also the ' hypotjTiipanic' articulation, ib. 29, for the mandible, so, 32. The neurapophyses of the third segment, ' o
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