Newman. — Notes on the Physiology and Anatomy of the Tuatara. 229 



joint itself is covered with mucli thinner skin and less tough tissue, and it 

 is at a joint that the tail hreaks. The tail bends only at the joints, the 

 inter-siDaces 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 to the 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 u^J the vertebral canal thereby 

 destroying the core. 



The tail may be fractured at almost any point ; if at 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 vertebrae ; repair began by 

 rounding of the broken end with compaction of cicatricial tissue. No 

 scales were formed on the new part or new vertebrae in it. 



Abdominal ribs. 



In addition to a number of vertebral ribs, the tuatara has twenty-five 

 or twenty-six (Giinther) 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 \ / , 

 forming a broad flat sole to support the viscera internally, and externally to 

 protect it from injury. Giinther considers " this system of bones is similar 

 to but essentially different from that observed in crocodiles and some 

 lizards (Chameleon, Polychrus, etc.), known as abdomirral ribs or abdominal 

 sternum, and considered to be the ossified inscriptiones tending of the 

 abdominal muscles." Giinther 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 Eolleston calls them " parostotic 

 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. If a 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 thm 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-niiuuto. ere expiration occurs. Owing to the peculiar shape of the 



