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 21 2 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
40