630 
MR. W. K. PARKER OK THE STRUCTURE AND 
Here it is plainly seen that the true “ epi-hyal ” element (“ hyo-mandibular ” of the 
Fish) is not distinct from the stapes, as in the Batrachia, but grafted upon it. In 
that group the stapes chondrifies some weeks, as a rule, before the “ epihyal,” which 
is late in its appearance, and then often cuts off a proximal piece, which wedges in 
between the stapes and the columella. Here the “ columella ” is manifestly a com¬ 
pound organ, both periotic and visceral. 
All its parts or regions can be made out, as in the Bird and Crocodile. The part 
grafted on the stapes (figs. 3 and 4, st.) is the “ medio-stapedial ” ( m.st .); the down- 
turned hook in which it ends is the “extra-stapedial” ( e.st .) ; and it has a knob turned 
towards the quadrate (q.), which is the “ supra-stapedial” is.st.) ; whilst the lower 
knob under the hook, turned towards the stylohyal, is the “ infra-stapedial ” (i.st.). 
With an extending knowledge of the parts in various groups, we can now harmonize 
the whole series of modifications seen in this part of the skull from the Cartilaginous 
Fishes up to Man. 
The 9th and 10th sections (figs. 5, 6) show the form of the auditory sac at its widest 
part, and its relation to the occipital arch. 
The supraoccipital ( s.o .) meets over the hind brain behind these sections; the basi- 
occipital (6.o.) is thick, hollow above, bulging below, and carries the notochord ( nc .) 
on its upper surface. In fig. 5 the stylohyal (st.h.) is seen in section; in fig. 6 the 
9th and 10th nerves (IX, X) are seen emerging between the capsule and the arch. 
These figures and descriptions will make the further metamorphosis of the skull, 
before hatching, to be easily understood. 
Sixth Stage. Skull of nearly-ripe Embryos of the Sand Lizard (Zootoca vivipara), 
1-g- inch in total length; head, -j inch long. 
The young of this species are very perfect at the time of hatching; they continue 
until then in the oviduct. (See Bell’s ‘British Reptiles,’ 1839, p. 32.) Tins highly- 
developed state of the young at birth (or hatching) is constant among the Reptiles, 
and also occurs in certain kinds of Birds; for instance, in the “Megapodidee,” ex. 
Talegalla Lathcimi. 
The skull of the adult having been described, this stage wants rather to be com¬ 
pared with that, than to have any very detailed description. 
The investing bones have all appeared, but they are thin at present, and do not 
perfectly cover the head, above ; indeed, the parietals (Plate 41, figs. 1 , 3 ,p.) are narrow, 
external bands, and they leave open a very large pentagonal fontanelle (fo.) : the 
frontals (/.) have met at the frontal suture. The double chain of superorbitals on 
each side (s.ob.) are small and irregular osseous points, and give but little promise at 
present of their future size and strength. 
But the premaxillaries, maxillaries, lachrymals, jugals, post-orbitals, supra-temporals, 
