stated that out of the 16 petioles which had been drawn in by their upper
ends, the more attenuated terminal portion of 7 had been previously
broken off by some accident.
_Triangles of paper_. Elongated triangles were cut out of moderately
stiff writing-paper, which was rubbed with raw fat on both sides, 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. {79}
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
39