318 REPORT—1846. 
neurapophysial relation to the sides of the prosencephalon,—we are led to 
carry our inquiries into an earlier period of their development than that ad- 
duced by Cuvier, as contravening their vertebral characters. Cuvier cites 
the figure 2, in pl. xxxv. of the ‘Osteogenia Foetuum’ of Kerkringius, as evi- 
dence of his statement of the developmental characters of the ‘ sphénoide 
antérieur.” That figure, however, exhibits the condition of the bone, when, 
although the median suture remains, each orbital ala has become anchylosed 
with the posterior sphenoid, and is likewise directly perforated by the optic 
nerve. The gelatinous cells of the anterior extremity of the notochord very 
early retrograde to the basioccipital region of the basis cranii, and the noto- 
chordal capsule alone is continued to the anterior extremity of the basis. 
This is converted into cartilage, 
and the osseous particles which Fig. 26. 
ultimately constitute the anterior 
sphenoid are deposited as follows : 
first a centre or nucleus appears, 
in each orbital ala, external to the 
hole by which the optic nerve 
passes through the primitive carti- 
lage (fig. 26, A, 10); soon after a 
second nucleus (76. B, 10) is esta- 
blished at the inner or mesial side 
of each optic foramen : these cen- 
tres form the foundation of the 
neurapophyses or orbitosphenoids, 
and ultimately coalesce around the 
optic nerve, as Kerkringius has 
depicted. Buta third pair of ossi- 
fic centres (ib. C, 9) is established 
behind the optic foramina between 
poe te oe henna (s). Phases of deyclapmeas the a Sphenoid bone: 
a single transverse bar (2b. D, 9), 
before coalescing with the orbitosphenoids in front, or with the basisphenoid 
behind, and that bar transitorily represents the centrum of the frontal vertebra. 
To the objection that such supposed centrum is developed from two points 
instead of one, the same reply may be made that was made before to a similar 
objection raised by Cuvier against the general homology of the basisphenoid ; 
which objection, as was then shown, would be equally valid against the uni- 
versally admitted homology of the body or centrum of the atlas. 
The frontal neurapophyses manifest in their development, each from two 
centres (fig. 26, B, C, 10), a transitory mark of vegetative repetition analogous 
to that which permanently characterizes the neurapophyses of the trunk-verte- 
bre in the sturgeon. 
Thus the evidence of development, when complete, tells for, rather than 
against the serial homology of the ‘sphénoide antérieur’ of Cuvier with the 
centrum and the neurapophyses of other vertebre ; and the more obvious 
and important characters of relative position to the other bones of their own 
segment, and to their homotypes in the contiguous segments, as well as to 
prosencephalic segment and characteristic nerves,—which characters have 
served to determine the special homologies of the coalesced bones in ques- 
tion (9,10) from man down to the fish,—concur with the developmental 
characters in establishing their general homology as centrum and neur- 
apophyses. 
