the formation of vegetable mould-第10部分
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so as to prevent their becoming excessively limp when exposed at
night to rain and dew。 The sides of all the triangles were three
inches in length； with the bases of 120 one inch； and of the other
183 half an inch in length。 These latter triangles were very
narrow or much acuminated。 ｛32｝ As a check on the observations
presently to be given； similar triangles in a damp state were
seized by a very narrow pair of pincers at different points and at
all inclinations with reference to the margins； and were then drawn
into a short tube of the diameter of a worm…burrow。 If seized by
the apex； the triangle was drawn straight into the tube； with its
margins infolded； if seized at some little distance from the apex；
for instance at half an inch； this much was doubled back within the
tube。 So it was with the base and basal angles； though in this
case the triangles offered； as might have been expected； much more
resistance to being drawn in。 If seized near the middle the
triangle was doubled up； with the apex and base left sticking out
of the tube。 As the sides of the triangles were three inches in
length； the result of their being drawn into a tube or into a
burrow in different ways； may be conveniently divided into three
groups： those drawn in by the apex or within an inch of it； those
drawn in by the base or within an inch of it； and those drawn in by
any point in the middle inch。
In order to see how the triangles would be seized by worms； some in
a damp state were given to worms kept in confinement。 They were
seized in three different manners in the case of both the narrow
and broad triangles： viz。； by the margin； by one of the three
angles； which was often completely engulfed in their mouths； and
lastly； by suction applied to any part of the flat surface。 If
lines parallel to the base and an inch apart； are drawn across a
triangle with the sides three inches in length； it will be divided
into three parts of equal length。 Now if worms seized
indifferently by chance any part； they would assuredly seize on the
basal part or division far oftener than on either of the two other
divisions。 For the area of the basal to the apical part is as 5 to
1； so that the chance of the former being drawn into a burrow by
suction； will be as 5 to 1； compared with the apical part。 The
base offers two angles and the apex only one； so that the former
would have twice as good a chance （independently of the size of the
angles） of being engulfed in a worm's mouth； as would the apex。 It
should； however； be stated that the apical angle is not often
seized by worms； the margin at a little distance on either side
being preferred。 I judge of this from having found in 40 out of 46
cases in which triangles had been drawn into burrows by their
apical ends； that the tip had been doubled back within the burrow
for a length of between 1/20 of an inch and 1 inch。 Lastly； the
proportion between the margins of the basal and apical parts is as
3 to 2 for the broad； and 2。5 to 2 for the narrow triangles。 From
these several considerations it might certainly have been expected；
supposing that worms seized hold of the triangles by chance； that a
considerably larger proportion would have been dragged into the
burrows by the basal than by the apical part； but we shall
immediately see how different was the result。
Triangles of the above specified sizes were scattered on the ground
in many places and on many successive nights near worm…burrows；
from which the leaves； petioles； twigs； &c。； with which they had
been plugged； were removed。 Altogether 303 triangles were drawn by
worms into their burrows： 12 others were drawn in by both ends；
but as it was impossible to judge by which end they had been first
seized； these are excluded。 Of the 303； 62 per cent。 had been
drawn in by the apex （using this term for all drawn in by the
apical part； one inch in length）； 15 per cent。 by the middle； and
23 per cent。 by the basal part。 If they had been drawn
indifferently by any point； the proportion for the apical； middle
and basal parts would have been 33。3 per cent。 for each； but； as we
have just seen； it might have been expected that a much larger
proportion would have been drawn in by the basal than by any other
part。 As the case stands； nearly three times as many were drawn in
by the apex as by the base。 If we consider the broad triangles by
themselves； 59 per cent。 were drawn in by the apex； 25 per cent。 by
the middle； and 16 per cent。 by the base。 Of the narrow triangles；
65 per cent。 were drawn in by the apex； 14 per cent； by the middle；
and 21 per cent。 by the base； so that here those drawn in by the
apex were more than 3 times as many as those drawn in by the base。
We may therefore conclude that the manner in which the triangles
are drawn into the burrows is not a matter of chance。
In eight cases； two triangles had been drawn into the same burrow；
and in seven of these cases； one had been drawn in by the apex and
the other by the base。 This again indicates that the result is not
determined by chance。 Worms appear sometimes to revolve in the act
of drawing in the triangles； for five out of the whole lot had been
wound into an irregular spire round the inside of the burrow。
Worms kept in a warm room drew 63 triangles into their burrows；
but； as in the case of the pine…leaves； they worked in a rather
careless manner； for only 44 per cent。 were drawn in by the apex；
22 per cent。 by the middle； and 33 per cent。 by the base。 In five
cases； two triangles were drawn into the same burrow。
It may be suggested with much apparent probability that so large a
proportion of the triangles were drawn in by the apex； not from the
worms having selected this end as the most convenient for the
purpose； but from having first tried in other ways and failed。
This notion was countenanced by the manner in which worms in
confinement were seen to drag about and drop the triangles； but
then they were working carelessly。 I did not at first perceive the
importance of this subject； but merely noticed that the bases of
those triangles which had been drawn in by the apex； were generally
clean and not crumpled。 The subject was afterwards attended to
carefully。 In the first place several triangles which had been
drawn in by the basal angles； or by the base； or a little above the
base； and which were thus much crumpled and dirtied； were left for
some hours in water and were then well shaken while immersed； but
neither the dirt nor the creases were thus removed。 Only slight
creases could be obliterated； even by pulling the wet triangles
several times through my fingers。 Owing to the slime from the
worms' bodies； the dirt was not easily washed off。 We may
therefore conclude that if a triangle； before being dragged in by
the apex； had been dragged into a burrow by its base with even a
slight degree of force； the basal part would long retain its
creases and remain dirty。 The condition of 89 triangles （65 narrow
and 24 broad ones）； which had been drawn in by the apex； was
observed； and the bases of only 7 of them were at all creased；
being at the same time generally dirty。 Of the 82 uncreased
triangles； 14 were dirty at the base； but it does not follow from
this fact that these had first been dragged towards the burrows by
their bases； for the worms sometimes covered large portions of the
triangles with slime； and these when dragged by the apex over the
ground would be dirtied； and during rainy weather； the triangles
were often dirtied over one whole side or over both sides。 If the
worms had dragged the triangles to the mouths of their burrows by
their bases； as often as by their apices； and had then perceived；
without actually trying to draw them into the burrow； that the
broader end was not well adapted for this purposeeven in this
case a large proportion would probably have had their basal ends
dirtied。 We may therefore inferimprobable as is the inference
that worms are able by some means to judge which is the best end by
which to draw triangles of paper into their burrows。
The percentage results of the foregoing observations on the manner
in which worms draw various kinds of objects into the mouths of
their burrows may be abridged as follows：…
Drawn
into the Drawn in； Drawn in；
Nature of Object。 burrows； by or by or
by or near near
near the the the
apex。 middle。 base。
Leaves of various kinds 80 11 9
… of the Lime； basal margin
of blade broad； apex
acuminated 79 17 4
… of a Laburnum； basal part of
blade as narrow as； or some…
times little narrower than
the apical part 63 10 27
… of the Rhododendron； basal
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
