Newman.—Notes on the Physiology and Anatomy of the Tuatara, 229 
joint itself is covered with much thinner skin and less tough tissue, and it 
is at a joint that the tail breaks. The tail bends only at the joints, the 
inter-spaces being rigid. The new tail is smooth, has no joints, is com- 
posed internally of cartilage, ‘like that of the lowest fishes," and by its 
external appearance can be at once distinguished from the older portion. 
In support of Knox's belief that owing tothe dragging away of the medulla 
spinalis the tail would not be reproduced, I may cite the fact that experiments 
have shown that certain lizards which reproduce their tails will not do so 
if a red-hot wire be passed some distance up the vertebral canal thereby 
destroying the core, 
The tail may be fractured at almost any point ;.if ʻi a distant point the 
animal soon recovers, but if near the pelvis it very frequently dies. In my 
full-grown tuatara the tail broke between the vertebrse; repair began by 
rounding of the broken end with compaction of cicatricial tissue. No 
scales were formed on the new part or new vertebra in it. 
Abdominal ribs, 
‘In addition to a number of vertebral ribs, the tuatara has twenty-five 
or twenty-six (Günther) abdominal ribs (Knox’s had twenty-five, mine 
twenty-five). They are double the number of the spinal ribs. To about 
the middle of each abdominal rib the spinal rib is attached, thus X — / 
forming.a broad flat sole to support the viscera internally, and externally io 
protect it from injury. Günther considers “ this system of bones is similar 
to but essentially different from that observed in crocodiles and some 
lizards (Chameleon, Polychrus, ete.), known as abdominal ribs or abdominal 
sternum, and considered to be the ossified inscriptiones tendine of the 
abdominal muscles." Günther also says, that “in no saurian, so far as 
we know at present, have they any relation to the external integuments.”’ 
Knox thought they were dermal, and Rolleston calls them * parostotie 
ossifications of the subcutaneous fibrous mesh." This opinion must be 
incorrect, for they lie imbedded in the rectus abdominis muscle. An 
examination of skeletons will incontestably prove that they are not dermal 
or exoskeletal but endoskeletal. 
Tuataras breathe slowly. As the abdomen and thorax are tightly bound 
in by abdominal ribs, the abdomen and thorax do not change their form, | 
the vertebral ribs alone moving during respiration. Ifa tuatara be watched 
while breathing, it will be seen that the greatest amount of motion is at the 
junction of the vertebral and abdominal ribs. The lungs (merely thin bags) 
run nearly the whole length of the thoracic and abdominal cavities. The 
tuatara inspires, its throat swells largely, then the capacious lungs. The 
walls of the trunk are then motionless for many seconds, sometimes upwards 
of half-a-minute, ere expiration occurs. Owing to the peculiar shape of the 
