EVOLUTION OF INTELLIGENT BEHAVIOUR 159 
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. 
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, 
and come to rest on the bottom. Then, taking the utmost 
care not to jar the dish or breathe upon the surface of the 
water, look at the Clepsine through a low magnifying lens, and 
see what happens when the surface of the water is touched 
with the point of a needle held vertically above the animal’s 
back. If the experiment is properly carried ont, it will be 
seen that the respiratory undulations Gf such movements 
happen to be going on) suddenly cease, and that the animal 
slightly expands its body and hugs the glass. Wait a few 
moments until the animal, recovering its normal composure, 
again resumes its respiratory movements. Then let the needle 
descend through the water until the point rests on the bottom 
of the dish at a little distance from the edge of the body. 
Again the movements will cease, and the animal will hug the 
glass with its body somewhat expanded. Now push the needle 
slowly along towards the leech, and notice as the needle comes 
almost in contact with the thin margin of the body, that the 
part nearest the needle begins to retreat slowly before it. 
* Wood’s Holl Biological Lectures (1898), p. 287. 
