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 
