TAILS 37 



so obvious. Take the lizard as an example. His tail 

 would appear at first sight to be of little or no service 

 to him, since he parts with it so readily. As a matter 

 of fact, the little reptile has many enemies ; of these, 

 the Indian crow is the chief. Now, when a crow attacks 

 a lizard, it naturally tries to seize him somewhere near 

 the middle. While the bird is striking at him, the rep- 

 tile starts to run away; the result is that the crow either 

 misses him or seizes him by the tail. If the latter 

 happens, the tail is swiftly detached, and the lizard 

 makes good his escape. 



A few animals possess tails which apparently serve 

 no useful purpose. These are exceedingly interesting 

 creatures, for, if their tails really are useless, they are 

 anomalies that threaten to upset all the theories of 

 biological science. I do not know the use of the tail 

 of the rat, or the mouse. Yet we may be tolerably 

 certain that in each case the organ has some use or it 

 would not exist. I employ the word "use" in a very 

 wide sense. I hold an organ to be useful to an animal 

 if it help its possessors to obtain a mate. 



Galton maintains that the action of Natural (or 

 Sexual) Selection is necessary to keep any organ up 

 to the mark ; that if the action of Natural Selection 

 is removed from any organ, that organ at once begins 

 to deteriorate. In other words, from the moment an 

 organ becomes useless to its possessor, that organ begins 

 to degenerate, and eventually disappears. Proofs of 

 this are seen throughout the realm of nature. 



Many animals which spend their lives in utter dark- 

 ness, whether in the depths of the ocean, or in caves, 



