228 Transactions. — Zoology. 



vertebras will not be reproduced. Giinther 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 

 XDrocess, this line corresponds to the external vertical furrow between two 

 verticelli." Knox, after carefully dissecting a specimen of Naultinus greiji, 

 writes " that the separation not, only occurred at a particular part of the 

 spine, but presented au 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 ., .. .. ..1 pair^j 



Abdominal ,, .. ,. .. . . 1 ,, I Total, 8 pieces." 



Lateral . ,, . . . . . . . . 2 ,, j 



"As," he continues, "I attentively observed the separation of the tail, I 

 found that a delicate white cord w^as gradually leaving a canal in the tail 

 portion. This I recognized to be the medulla spinalis, and necessarily 

 rendered, in my behef, 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 Ivnox'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. As in 

 Knox's KauUimis, 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 then- taUs 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 



