70 THE STUDY OF ANIMAL LIFE CHAP. 



healing membrane which prevents bleeding. It is not 

 deliberately or reflectively that the crab has learned 

 that it is better that one member should perish than 

 that the whole life should be lost, but the gradations of 

 modes of self-amputation suggest that there may have 

 been long ago much more awareness and control in the 

 process than there is now. 



Not a few insects and spiders readily surrender their 

 legs when captured. Among Molluscs a surrender of 

 parts has been recorded of Harpa ventricosa, Doris cruenta, 

 Stenopus, some species of Helix, the razor-shell Solen ; 

 while it is well known that male cuttle-fishes sometimes 

 part with one of their arms for special sexual purposes. A 

 great many ' ' worms ' ' break very easily, and the severed 

 parts are sometimes able to regrow the whole organism. 



Among the Echinoderms the tendency to disrupt is 

 exhibited to an extraordinary degree. Thus Prof. 

 Preyer has shown that the seven-rayed starfish (Asterias 

 tenuispina) surrenders its arms with great readiness, often 

 giving off three or four at a time. But each ray may 

 reproduce an entire starfish. Professor Edward Forbes 

 tells how a specimen of Luidia, which he had dredged, 

 was disappearing over the side of the boat when he 

 caught it by one of its arms ; it surrendered the arm 

 and escaped, giving ' a wink of derision ' with one of 

 its eyes. Brittle-stars (Ophiuroids) of many kinds are 

 true to their popular name, and the Crinoids are not less 

 disruptive. Not only are the arms readily given off, but 

 these break into many fragments. There can be no 

 doubt that this habit, combined with the marvellous 

 power of regrowth which these animals possess, is of 

 great protective value, while it is also probable, in regard 

 to both Echinoderms and some worms, that the disrup- 

 tion of parts may really increase the number of individuals. 



Many animals when alarmed " feign death," passing 

 into a rigid cataleptic state, akin to the state of animal 

 hypnosis which can be experimentally induced in some 

 mammals, birds, reptiles, and amphibians. Many of the 

 lower creatures, such as small crustaceans, ' stop dead ' 

 when there is a sudden change in the nature of their 



