220 
Transactions of the 
On each side, in the indifferent tissue that covers this rod above, 
the prae-maxillaries are found, as small oval patches of osteoblasts 
(Fig. 3, p. n., p. x.). The cartilaginous cranium is already well 
formed, and the auditory sacs ( au .) with their enclosed otoliths (ot.) 
are well seen in this delicate skull when examined as a transparent 
object. The pituitary space (pg.) is still freely continuous with the 
space in which the notochord ( n.c .) lies — “the posterior basi-cranial 
fontanelle ” — hut the halves of the “ investing mass ” (i. v.) have 
united on each side with the auditory mass, and also with each 
other behind ; where they have formed the bilobate occipital condyle 
(o. c.). From the investing mass on each side, a little in front of the 
condyle, there is a crest of cartilage, the “ ex-occipital ” (e. o.), which 
is growing towards its fellow in the “ super-occipital ” region (s. o.), 
and is becoming coalesced to the hinder margin of the auditory sac. 
A side view of the cranio-facial axis, from the “ sella turceca ” 
forwards, is shown in Fig. 4 ; it takes in the whole trabecular bar. 
Here we see how large the terminal cartilage is, notwithstanding 
its temporary character, and also that the trabeculae have sent 
upwards a crest of cartilage which is continuous with the keel 
growing from the cranial floor and nasal roof from the optic 
foramen (2) to the commencement of the pre-nasal rostrum (p. n.). 
Not only has continuous metamorphosis of the mother-cells into 
cartilage made these various morphological parts one, but the roof 
of the nasal sacs and the floor of the hemispheres have undergone 
the same change. Between the eye and nose the nasal wall has 
become a large uniform plate of cartilage ; this is the “ pars plana ” 
(p.p.) or “ ecto-ethmoid.” A transverse section through this region 
(Fig. 5) shows the relation of the “ ecto- ” to the “ meso-ethmoid.” 
In another section (Fig. 6) the septum nasi is cut through, and 
the ali-septal cartilages are seen each to give off an elegant scroll 
with two turns : this is the equivalent of the human “ inferior 
turbinal,” although its position is in front of and not below the true 
olfactory region. A section made between the eye-balls (Fig. 7) 
shows the cartilaginous continuity of the two trabeculae ; their 
ascending crests, the anterior sphenoidal keel (prae-sphenoid), and 
the “ orbito-sphenoidal laminae.” 
Most of the investing bones can now be seen. I have already 
spoken of the prae-maxillaries, and others will be better shown in an 
embryo more advanced, but four out of five of the mandibular 
splints can now be well observed. On the inner side of the 
“ articulo-Meckelian rod ” (Fig. 8, cr .) the “ coronoid ” is seen at 
the top ; and the “ angulare ” (ang.) on the inner side, and part 
of the “ surangulare ” (s. ag.) below. On the outer side (Fig. 9) 
the whole of the large “ surangulare ” is shown, as also, much 
further forwards, the “ dentary ” (cl) : the “ splenial ” (sp.) is shown 
in a more advanced stage. 
