:::;::*f TWO BIRD -LOVERS IN MEXICO 



they dove-tail into one another. So now it is clear that, 

 if an enemy — myself in this instance — grasps the 

 tail (which is the last exposed part of the animal as it 

 dives into its hole), the violent struggles of the Iguana 

 are sufficient to complete the crack which the wedge 

 of cartilage always holds open, and the short muscles, 

 slipping from their dove-tailed positions, give way, and 

 thus separate the Eioana — as the Mexican tongue 

 pronounces it — and his tail ! 



If this were all, an Iguana could have but one such 

 chance of escape in his life, and if the break came 

 between the tail-bones instead of across the middle of 

 one of them, the creature would indeed go curtailed 

 through life. But by another kindly provision of Na- 

 ture, the exposed cells immediately begin to grow and 

 before long, behold, a new tail ! But in reality a sham 

 one, for from the stump there grows out a long, un- 

 jointed rod of cartilage, not bone, with but few muscles, 

 and skin which is covered with very small s^^ines. But 

 little the Iguana cares about the internal structure of 

 his new appendage ; the fact that it is there, and may 

 again be cast off in case of dire extremity, is all sufficient 

 to him. It is a most interesting fact that, as the newly 

 regenerated rod of cartilage recalls the condition of 

 bone in the embryonic state, so the more simple ar- 

 rangement of spines on the new skin sometimes harks 

 back to an ancestral condition. The new tail thus bears 

 upon it the shadow of the distant past. 



-x^ 232 ■>> 



