106 BRITISH LIZAEDS 



detached from the body, requires a division of the soft 

 parts surrounding it, as well as a fracture of the bone. 

 It therefore may be concluded, theoretically, that the 

 dropping of the lizard's tail must depend upon the 

 pecuhar arrangement of the muscles and integument 

 quite as much, if not more than, upon the ease with 

 which the vertebrae are enabled to break across. 



The first problem which presents itself in this 

 connection is this. Seeing that in most animals 

 possessed of long tails the muscles are attached from 

 one vertebra to another, allowing of a certain amount 

 of intervertebral movement, but keeping the tail, as a 

 whole, attached to the body even if a fracture of 

 a vertebra occurs, what special muscular arrangement 

 exists in those hzards which drop their tails when 

 this accident happens ? Secondly, even if by some 

 anatomical arrangement the muscles do not keep the 

 tail attached to the body, how is it that the skin or 

 integument always breaks all round the circumference 

 of the tail exactly over the point of the fractured 

 vertebrae ? 



(The species of lizards first used to investigate 

 these points were Aiiguis fragilis, the slow-worm, and 

 Lacerta viridis, the green lizard, of the Continent and 

 Channel Islands.) 



1. Angicis fragilis, the Slow-worm. 



Selecting a specimen from my collection, I proceeded 

 to carefully break off a portion of the tail. It was 



