WORMS AND CCELENTERATA 267 



moles, shrew-mice, birds, lizards, amphibians, insects, 

 and many others, it is the myriapods, especially, that 

 pursue it into its own tubes. We often see the worm 

 creep in terror from its passages in full daylight to 

 escape these dreaded enemies. 



The danger of being captured is less fatal to the 

 earth-worms than to other animals, as they have a 

 great power of regeneration, and can lose a part of their 

 body without perishing, because they can replace it. 

 One can cut a worm into two parts, and one part — 

 often the second one as well — will always regenerate the 

 lost piece. If it is cut into several pieces, there is never 

 more than one new animal, and often none at all ; and if 

 it is cut longitudinally into two halves both of them 

 very soon die. 



Here again we see that the power of regeneration 

 is an adaptive phenomenon, and does not act in rare 

 situations. What generally happens is that a piece is 

 torn off an earth-worm, and the rest of it retreats 

 underground. This mutilation would soon extinguish 

 the animals if it were fatal to them ; and the other 

 injuries happen too rarely for natural selection to have 

 provided a remedy against them. 



In the near relatives of the earth-worm, that live in 

 water, such as the lumbriculus, the regenerative power 

 is much higher. One of these animals has been cut 

 into fourteen pieces, and thirteen of these formed new 

 worms. These animals are devoured on all sides, and 

 their enemies, the water-insects, have sharp jaws with 

 which they cut pieces out of them. There are various 

 species of aquatic worms, and in each of them it can be 



