60 Proceedings of the Royal Physical Society. 



clear views. It is safer 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 Lancelet, — (Amphioxus lanceolatus — Brancliiostoma — 

 Owen). This lowest vertebrate type was classed as an inver- 

 tebrate annelid till it was shown by Goodsir (Roy. 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-eneephalon, 

 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 in verte- 

 bralia, places the Lancelet in a higher relation than its 

 former associates — the Entozoa. 



The centro-chord, though not the spinal 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, Dumeril, and others ; and since their day, in this 



