FRAGILITY OF THE TAIL IN LIZARDS 107 



at once evident that while the integument ruptured 

 readily round the circumference of the lower half (the 

 ventral half) of the tail at the point of fracture, it did 

 not do so nearly so easily on the dorsal aspect. In 

 fact, some degree of force was necessary to complete 

 the division of the skin all round. But by bending 

 the two halves of the tail, as one would bend a stick 

 across the knees, the fracture was completed. The 

 structures thus separated in the following order : — 



First, the ventral integument ; 



Then the ventral muscles ; 



Then the lateral integument and muscles on 

 each side ; 



Then the dorsal muscles ; 



Lastly, the dorsal integument. 

 This indicates the degree of ease with which the 

 parts separated, the ventral aspect rupturing most 

 easily, the dorsal remaining intact the longest. The 

 first thing that struck me was that the initial point of 

 separation was in the skin, not, apparently, in the 

 vertebra, and one naturally wondered whether this 

 corresponded to the position of the cartilaginous 

 septum. The next thing that compelled notice v/as 

 that the two separated ends of the tail — the proximal 

 and the distal ends — presented a marked contrast. 

 The proximal end, still of course attached to the body, 

 exhibited eight muscles which had been separated 

 from their attachments to the distal portion, giving 

 the proximal end a stellate appearance ; while the 



