THE SCHOOL OF THE SHORE 49 
itself again. One of the hermit crabs (Pagurus 
cuanensis) in deeper water has its borrowed 
shell frequently surrounded by a bright orange 
sponge (Suberites domuncula), with a strong 
odour, a disagreeable taste, and countless 
flinty needles—which fishes naturally leave 
alone! 
A LIMB FOR A LIFE 
Many different kinds of animals, especially 
those with rather lanky limbs, practise a curi- 
ous kind of surrender—a limb for a life. And 
what they surrender as a ransom for their life 
they can regrow at leisure. 
This is well illustrated by many star-fishes. 
If an arm is pinned down by a stone, or seized 
by an enemy, or if a sea-slug has settled on an 
arm and cannot be dislodged, the star-fish 
manages to break off the arm at the base. In 
so doing it is behaving as we behave when we 
draw back our finger from a very hot plate, or 
shut our eye when a stone is about to strike it, 
or cough when a crumb of bread threatens to 
“oo down the wrong way.” We do not think 
about doing any of these things nor exercise 
our will; what we do is called a reflex action, 
carried out by means of pre-arranged linkages 
