EVOLUTION OF INTELLIGENT BEHAVIOUR 157 
The greatest distance I have watched a limpet reach from 
its home was twenty-two inches. But I have found them at a 
distance of three feet from their scars—that is to say, from 
those to which they fitted perfectly. This was on a large flat 
surface. 
When they move, the tentacles are projected out beyond 
the shell, and keep on touching and slightly adhering to the 
rock. On reaching the scar they carefully feel round it with 
the tentacles. By excision of these feelers Professor Davis was 
led to conclude that it is not through their instrumentality that 
the limpet finds its way back to its particular scar. But 
I am inclined to question these results. At any rate, further 
observations and experiments are needed to settle the point. 
Snails will also return to special dark hollows or crannies 
in the wall after their foraging excursions. Such behaviour 
in molluscs affords evidence of something more than instinct. 
In popular speech, we should say that there is memory of the 
locality. And in any case it is difficult to interpret the facts 
without the assumption that the animals are conscious, and 
that re-presentative states are evoked through the mediation of 
presentative sense-impressions. And such re-presentative states 
are the foundation-stones of experience, which forms the basis 
on which intelligent behaviour is grounded. 
The most highly developed molluscs are the cephalopods. 
They have long sensitive mobile arms with which they feel for 
and capture their prey. ‘‘ Now Schneider observed,” writes 
Dr. Stout,* “a very young octopus seize a hermit-crab. The 
hermit-crab covers the shell in which it takes up its abode 
with stinging zoophytes. Stung by these, the octopus imme- 
diately recoiled and let its prey escape. Subsequently it was 
observed to avoid hermit-crabs. Older animals of the same 
species managed cleverly to pull the crab out of its house 
without being stung.” Such cases afford evidence of profiting 
by experience through the exercise of intelligence. 
Darwin’s careful observations on the manner in which 
earthworms drag leaves into their burrows seem to show that 
* “Manual of Psychology,” p. 257. 
