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 
(Phalangidz), 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 
