60 Proceedings of the Boyal Physical Society. 
clear views. It is saler to examine the progress of ossifica- 
tion in the adult species, as seen in the animal scale. 
Keeping in view the simple scheme of the foregoing com- 
munication where the term " vertebra " is restricted to the 
kaulon or central stem of the vertebral column and the 
peri-neural or meta-vertebral portion of the segment, re- 
stricted to the neur-arcs of the tunnel of the cerebro-spinal 
axis and the peri-splanchnic and hemal or pro-vertebral 
part of the segment, and instead of the complex apophysal 
terms of Owen using the common terms of the medical 
schools of anatomy for the elemental component parts of 
the laminae, whether simple as in the ribs and maxilla or 
lower jaw, or in those more complex laminae of the limbs, — 
where the carpus and tarsus seem to be the repetition of 
the laminae, branching from the distal joint of the lamella 
or second part. 
The vertebrate skelon consists of a central chain of bones 
in its early condition, discoid in form, enveloped in a mem- 
branous tissue forming the centro-chord as exhibited in 
the Lancelot, — {A mphioxus lanceolatus — Branchiostoma — 
Owen). This lowest vertebrate type was classed as an inver- 
tebrate annelid till it was shown by Goodsir (Eoy. Soc. Edin. 
Transactions, xv. 1), and Owen (in his Lectures, ii. p. 171), to 
possess a feeble median linear centro-chord arrangement ; 
most distinct anteriorly, where it is cylindrical, it is con- 
tinued to the very point of the animal, beyond the early 
development of the olfactory and optic nerves, the first dawn 
in vertebralia of the Mes-encephalon and Pros-enc^ephalon, 
and accompanied by the trigeminal nerves from the Par- 
encephalon or upper part of the Myelon. The centro-chord 
supporting the neural axis and placed above the visceral 
and hemal axes, instead of lying below as in the inverte- 
bralia, places the Lancelot in a higher relation than its 
former associates — the Entozoa. 
The centro-chord, though not the spioal column, is ad- 
mitted to be at least the nucleus of the chain of vertebral 
centres, which has been received as proving the vertebral 
condition of the cranium, first propounded by Goethe, Oken, 
Spix, Dumcril, and others ; and since their day, in this 
