A LIMB FOR A LIFE 167 
sisting in a prolonged endeavor along a line which 
is certainly not that of least resistance, which leads 
to a reward not immediately, but only eventually. 
Perhaps Nature would not have put her natural 
selection stamp of approval on the asteroid’s 
autotomy if individual starfishes had not approved 
of it themselves. We are not prepared indeed to 
say what form the brainless creature’s approval 
might take, but we get an indication of it perhaps 
in approvals given by our subconscious self. Quite 
in the opposite direction is another saving-clause, 
that cases of a rat or a stoat cutting itself free from 
a trap by amputating a limb, belong to a category 
different from and higher than that of starfishes or 
crabs which illustrate typical autotomy. 
The highest level at which autotomy is practised 
is among lizards, many of which need but little 
provocation to induce them to surrender their tail 
to their assailant—an expedient that often saves 
their life. The specific name of our British limbless 
lizard (Anguis fragilis) registers the uncanny readi- 
riess with which it surrenders the tail of its snake- 
like body. That lizards have taken ages to bring 
their life-saving curtailment to perfection seems 
probable, especially when we notice that in many 
forms there is a special breakage area, and that 
a weak line has been established affecting skin, 
muscles, connective tissue, and backbone. Up the 
middle of the vertebra there is a soft zone, the 
breakage plane, across which the tail snaps in the 
autotomy. What is lost by the amputation can 
