EVOLUTION OF INTELLIGENT BEHAVIOUR 159 
ways to draw in objects, and at last succeed in some one 
way ;” that is to say, they profit by experience based on the 
method of trial and failure. But Darwin adds that the 
evidence he obtained shows “that worms do not habitually 
try to draw objects into their burrows in many different ways.” 
And he seems to attribute to them an almost rational power of 
dealing with the circumstances in the light of general con- 
ceptions. “If worms,” he says, “are able to judge, either 
before drawing or after having drawn an object close to the 
mouths of their burrows, how best to drag it in, they must 
acquire some notion of its general shape. ‘This they probably 
acquire by touching it in many places with the anterior 
extremity of their bodies, which acts as a tactual organ. It 
may be well to remember how perfect the sense of touch 
becomes in a man when born blind and deaf, as are worms. 
If worms have the power of acquiring some notion, however 
rude, of the shape of an object and of their burrows, as seems 
to be the case, they deserve to be called intelligent ; for they 
then act in nearly the same manner as would a man under 
similar circumstances.” 
Such power of perceiving the relation of the shape of 
a leaf or other object to the form of the burrow is presumably 
beyond the reach of an earthworm. It may be regarded as 
more probable that the earthworm inherits an instinctive 
tendency to draw down objects in special ways, and that this 
is subject to some modification under the play of experi- 
ence, without the formation of anything so psychologically 
complex as a general notion, however rude. In any case the 
behaviour of earthworms in closing their burrows seems to 
afford indications of something more than instinct—of that 
profiting by the results of experience which characterizes 
intelligent procedure. More than this we cannot say. 
Professor Whitman * has made some interesting observa- 
tions on the leech Clepsine. ‘* Place the animal,” he says, ‘ in 
a shallow, flat-bottomed dish, and leave it for a few hours or 
a day, in order to give it time to get accustomed to the place, 
* Wood’s Holl Biological Lectures (1898), p. 287. 
