:::::::::C ALONG THE STREAM OF DEATH m::::::::: 



relaxing of the strain and I fell backward, while the 

 Iguana shot ahead into a steep hollow among the 

 rocks. I had nine inches of tail in my hand and the 

 Iguana seemed not a whit discommoded by his loss. 

 After a hard struggle I secured him and kept him still 

 long enough to photograph him, together with his 

 discarded member, after which he rushed rapidly off 

 to his hole. The entire reptile measured twenty -eight 

 inches, and we realized that he was thus able to cast 

 off one third of his entire length with imj) unity. 



This breaking off of the long tails of lizards is a 

 most interesting process, besides being of the greatest 

 value to the creatures themselves. Before an lof-uana 

 emerges from the tgg, its skeleton is not bony, but 

 formed of a jelly-like substance which soon becomes of 

 the consistency of hard gristle. This is called cartil- 

 age, and later, when the true bone is deposited, a wad 

 or pad of this cartilage remains unossified between each 

 of the vertebrae, forming the backbone. This is true of 

 almost all the higher animals, but, in the tail-bones 

 of the lo-uana, a little wedo-e of cartilao-e is found, ex- 

 tending almost across the centre, or the centrum, as it 

 is called, of each bone. This, of course, causes a great 

 weakness of the whole bone, and if such a condition 

 existed in the upper back or neck, it would, indeed, be 

 unfortunate for the lizard. But in the tail it proves an 

 admirable safeguard. Here the muscles are very thick 

 and short, and opposite the centre of each bone, and 



<4 231 ^ 



