168 SECRETS OF ANIMAL LIFE 



be regrown at leisure, though not with the original 

 finish. Newts and salamanders (and the tadpoles 

 of frogs and toads) have great powers of regrowing 

 parts that have been bitten off, but, so far as we 

 know, lizards are the only backboned animals that 

 show autotomy. The phenomenon is seen again 

 among mollusks, not a few of which give off pieces 

 of their body. There is the very curious case of 

 many male cuttlefishes which give away an " arm " 

 in marriage the discharged member being described 

 by some old zoologists as a separate creature called 

 " Hectocotylus." This instance should perhaps be 

 kept by itself, but it shows that the capacity of 

 surrendering parts can be utilized towards various 

 ends. 



Some zoologists have tried to restrict the term 

 " autotomy " to the surrender of what should 

 normally be retained, but it does not seem practi- 

 cable to maintain this strict usage. Many of the 

 sea-slugs, like Tethys, though captured ever so 

 gently, proceed to disembarrass themselves of finger- 

 like processes on their back strange sops to 

 Cerberus. Many worms also show a strong tendency 

 to self -mutilation when they find themselves in the 

 unusual conditions of capture. One throws off its 

 tentacles, another its pharynx; one offers you its 

 head and another its tail. We look on with helpless 

 chagrin while a fine specimen of a ribbon-worm, 

 say Cerebratulus, lying unharmed in a basin of clean 

 sea-water, breaks with strong muscular contractions 

 into inch-long pieces. There may be some intense 



