$98 ; Transactions.—Z oology. 
vertebre will not be reproduced. Günther thinks that the tails of Hatteria 
are less easily broken than those of other lizards, because its external 
_ Structures are less distinctly divided into segments or verticelli and 
strengthened by a thick layer of strong subcutaneous tissue :—'* The 
epiphysial line passing through the middle and behind the transverse 
process, this line corresponds to the external vertical furrow between two 
verticelli." Knox, after carefully dissecting a specimen of Naultinus greyi, 
writes “ that the separation not only occurred at a particular part of the 
spine, but presented an obstacle to its regeneration which appeared to me, 
and still appears, impossible. I found the divided or separated surface 
finely dove-tailed, the one (proximal extremity of the skin) presenting no 
dentations but a perfectly smooth margin, the scales surrounding the part 
arranged in symmetrical order, whilst on the separated part or tail eight 
wedge-shaped processes projected beyond the skin of the tail. These eight 
processes were entire and not caused by a tearing process, but were 
arranged in pairs:— 
Dorsal margin  . Ks a 03 pair 
Abdominal ,, em is e» wrk p lza 8 pieces.” 
Lateral z 
i Fi xs ee ee 4 5 
“ As,” he continues, “I attentively observed the separation of the tail, I 
found that a delicate white cord was gradually leaving a canal in the tail 
portion. This I recognized to be the medulla spinalis, and necessarily 
rendered, in my belief, the power of reproduction still less possible.” 
In a young tuatara that I possessed similar conditions obtained; the 
processes were the caudal muscles, primordial, confluent at the base, and 
afterwards dividing into eight processes with tendinous endings. Contrary 
to what obtained in Knox’s Naultinus, the processes were attached to the 
trunk and not to the tail portion. The processes were bare because the 
skin had retracted. Evidently the muscles had given way at the point of 
insertion into a vertebra. The muscles were arranged in a whorl. Asin 
Knox’s Naultinus, there certainly was no division through a vertebra. I 
apprehend that different forms of violence would give rise to different forms 
of fracture, and that though that through the epiphysial line might be by 
far the most common, yet it need not always occur. That the tails do 
occasionally fall off because of excessive muscular action is shown by the - 
fact that lizards drop their tails when greatly frightened. On the other 
hand, if a lizard fall to the floor from table or roof, fracture through a 
vertebra would in all probability result. 
Cuvier wrote that the tails of certain lizards are reproduced, but 
without spines or creases. This corresponds with what is found in the 
. tuatara and Naultinus. The tails of the tuatara are divided into numerous 
joints, the skin between each joint being like that of the trunk, but the 
