158 INTELLIGENT BEHAVIOUR 
these annelids act intelligently, and deal with leaves of different 
shapes in different ways. The leaves of Pine trees, consisting 
of two needles arising from a common base, were almost 
invariably drawn down by seizing this basal point of junction ; 
while the leaves of the Lime were, in 79 per cent. of the 
cases examined, drawn down by the apex; in only 4 per 
cent. by the base; and in the remaining 17 per cent. by 
seizing some intermediate portion. On the other hand, the 
leaves of the Rhododendron, in which the basal part of 
the blade is often narrower than the apical part, were in 
66 per cent. of the observations drawn down by the narrower 
base. Triangles of paper were in the majority of cases 
seized by the apex. Commenting upon his observations, 
carried out with great care under experimental conditions, 
Darwin says,* “ As worms are not guided by special instincts 
in each particular case, though possessing a general instinct to 
plug up their burrows, and as chance is excluded, the next 
most probable conclusion seems to be that they try in different 
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 
* « Vegetable Mould and Earthworms,” p. 95, 
