A LIMB FOR A LIFE 169 



disturbance of metabolism which we do not under- 

 stand; or it may be that we are simply witnessing 

 an extreme tetanic exhibition of what occurs in a 

 less drastic way in ordinary life and with life-saving 

 results. For minor losses are soon made good and 

 parts may become wholes. In many simple worms 

 the periodic surrender of a posterior piece is a 

 regularized mode of multiplication; in the Palolo 

 worm, which burrows in the coral-reefs, nearly the 

 whole of the body is broken off at the breeding 

 season and bursts in the water, liberating tens of 

 thousands of germ-cells, while the head remains in 

 the rock and makes a new body by and by. Among 

 starfishes, brittle-stars, feather-stars, and sea- 

 cucumbers there is an extraordinary prevalence of 

 autotomy. A starfish may jerk off each of its five 

 arms seized in succession; it may cast off an injured 

 or parasitized arm; in rare cases there is multiplica- 

 tion by division. Sea-cucumbers discharge their 

 viscera in the spasms of capture and may thus 

 escape from an astonished foe. The replacement of 

 the food-canal is sometimes accomplished in ten 

 days, though it may take as many weeks. The 

 heart-urchin often gives off its snapping spines when 

 they nip the skin of some molester. 



One often sees among the stubble very interesting, 

 somewhat spider-like creatures called harvestmen 

 (Phalangidae), which move swiftly (in the evening 

 especially) on extraordinarily lank legs, over twenty 

 times the length of the body. They hunt mostly 

 by night, killing and sucking small insects and 



