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part of blade often narrower
than the apical part 34 。。。 66
… of Pine…trees； consisting of
two needles arising from a
common base 。。。 。。。 100
Petioles of a Clematis；
somewhat pointed at the apex；
and blunt at the base 76 。。。 24
… of the Ash； the thick basal
end often drawn in to serve
as food 48。5 。。。 51。5
… of Robinia； extremely thin；
especially towards the apex；
so as to be ill…fitted for
plugging up the burrows 44 。。。 56
Triangles of paper； of the
two sizes 62 15 23
… of the broad ones alone 59 25 16
… of the narrow ones alone 65 14 21
If we consider these several cases； we can hardly escape from the
conclusion that worms show some degree of intelligence in their
manner of plugging up their burrows。 Each particular object is
seized in too uniform a manner； and from causes which we can
generally understand； for the result to be attributed to mere
chance。 That every object has not been drawn in by its pointed
end； may be accounted for by labour having been saved through some
being inserted by their broader or thicker ends。 No doubt worms
are led by instinct to plug up their burrows； and it might have
been expected that they would have been led by instinct how best to
act in each particular case； independently of intelligence。 We see
how difficult it is to judge whether intelligence comes into play；
for even plants might sometimes be thought to be thus directed； for
instance when displaced leaves re…direct their upper surfaces
towards the light by extremely complicated movements and by the
shortest course。 With animals； actions appearing due to
intelligence may be performed through inherited habit without any
intelligence； although aboriginally thus acquired。 Or the habit
may have been acquired through the preservation and inheritance of
beneficial variations of some other habit； and in this case the new
habit will have been acquired independently of intelligence
throughout the whole course of its development。 There is no a
priori improbability in worms having acquired special instincts
through either of these two latter means。 Nevertheless it is
incredible that instincts should have been developed in reference
to objects； such as the leaves of petioles of foreign plants；
wholly unknown to the progenitors of the worms which act in the
described manner。 Nor are their actions so unvarying or inevitable
as are most true instincts。
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 many different ways to draw
in objects； and at last succeed in some one way。 But it is
surprising that an animal so low in the scale as a worm should have
the capacity for acting in this manner； as many higher animals have
no such capacity。 For instance； ants may be seen vainly trying to
drag an object transversely to their course； which could be easily
drawn longitudinally； though after a time they generally act in a
wiser manner； M。 Fabre states ｛33｝ that a Sphexan insect
belonging to the same highly…endowed order with antsstocks its
nest with paralysed grass…hoppers； which are invariably dragged
into the burrow by their antennae。 When these were cut off close
to the head； the Sphex seized the palpi； but when these were
likewise cut off； the attempt to drag its prey into the burrow was
given up in despair。 The Sphex had not intelligence enough to
seize one of the six legs or the ovipositor of the grasshopper；
which； as M。 Fabre remarks； would have served equally well。 So
again； if the paralysed prey with an egg attached to it be taken
out of the cell； the Sphex after entering and finding the cell
empty； nevertheless closes it up in the usual elaborate manner。
Bees will try to escape and go on buzzing for hours on a window；
one half of which has been left open。 Even a pike continued during
three months to dash and bruise itself against the glass sides of
an aquarium； in the vain attempt to seize minnows on the opposite
side。 ｛34｝ A cobra…snake was seen by Mr。 Layard ｛35｝ to act much
more wisely than either the pike or the Sphex； it had swallowed a
toad lying within a hole； and could not withdraw its head； the toad
was disgorged； and began to crawl away； it was again swallowed and
again disgorged； and now the snake had learnt by experience； for it
seized the toad by one of its legs and drew it out of the hole。
The instincts of even the higher animals are often followed in a
senseless or purposeless manner： the weaver…bird will
perseveringly wind threads through the bars of its cage； as if
building a nest： a squirrel will pat nuts on a wooden floor； as if
he had just buried them in the ground： a beaver will cut up logs
of wood and drag them about； though there is no water to dam up；
and so in many other cases。
Mr。 Romanes； who has specially studied the minds of animals；
believes that we can safely infer intelligence； only when we see an
individual profiting by its own experience。 By this test the cobra
showed some intelligence； but this would have been much plainer if
on a second occasion he had drawn a toad out of a hole by its leg。
The Sphex failed signally in this respect。 Now if worms try to
drag objects into their burrows first in one way and then in
another； until they at last succeed； they profit； at least in each
particular instance； by experience。
But evidence has been advanced showing that worms do not habitually
try to draw objects into their burrows in many different ways。
Thus half…decayed lime…leaves from their flexibility could have
been drawn in by their middle or basal parts； and were thus drawn
into the burrows in considerable numbers； yet a large majority were
drawn in by or near the apex。 The petioles of the Clematis could
certainly have been drawn in with equal ease by the base and apex；
yet three times and in certain cases five times as many were drawn
in by the apex as by the base。 It might have been thought that the
foot…stalks of leaves would have tempted the worms as a convenient
handle； yet they are not largely used； except when the base of the
blade is narrower than the apex。 A large number of the petioles of
the ash are drawn in by the base； but this part serves the worms as
food。 In the case of pine…leaves worms plainly show that they at
least do not seize the leaf by chance； but their choice does not
appear to be determined by the divergence of the two needles； and
the consequent advantage or necessity of drawing them into their
burrows by the base。 With respect to the triangles of paper； those
which had been drawn in by the apex rarely had their bases creased
or dirty； and this shows that the worms had not often first tried
to drag them in by this end。
If worms 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 serves as a tactile
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。
To sum up； as chance does not determine the manner in which objects
are drawn into the burrows； and as the existence of specialized
instincts for each particular case cannot be admitted； the first
and most natural supposition is that worms try all methods until
they at last succeed； but many appearances are opposed to such a
supposition。 One alternative alone is left； namely； that worms；
although standing low in the scale of organization； possess some
degree of intelligence。 This will strike every one as very
improbable； but it may be doubted whether we know enough about the
nervous system of the lower animals to justify our natural distrust
of such a conclusion。 With respect to the small size of the
cerebral ganglia； we should remember what a mass of inherited
knowledge； with some power of adapting means to an end； is crowded
into the minute brain of a worker…ant。
Means by which worms excavate their burrows。This is effected in
two ways； by pushing away the earth on all sides； and by swallowing
it。 In the former case； the worm inserts the stretched out and
attenuated anterior extremity of its body into any little crevice；
or hole； and then； as Perrier remarks； ｛36｝ the pharynx is pushed
forwards into this part； which consequently swells and pushes away
the earth on all sides。 The ant