Plants That Feed on Insects. 27 
raw beef, the tentacles of healthy leaves, from within to 
without, but in periods of time varying from six to eight 
or nine hours, clasp firmly the beef, almost concealing it 
from view. Equally vigorous leaves, however, made no 
move towards clasping a bit of dry chalk, a chip of flint, or 
alump of earth. Bits of raw apple cause a curving of the 
tentacles, but very few of the glands are seen touching them. 
It would seem, therefore, that these plants are really carniv- 
orous, preferring animal substances, which they, by the aid 
of some ferment analogous to pepsin, which is secreted by 
the glands, are able to absorb. A minute quantity of already 
soluble animal matter is the exciting cause, and this must 
be taken in by the glands, or there is no secretion of the 
fermenting material. 
In all ordinary cases the glands alone are susceptible to 
excitement. When excited, they do not themselves move 
or change form, but transmit a motor impulse to the bend- 
ing part of their own and adjoining tentacles, and are thus 
carried towards the centre of the leaf. Stimulants applied 
to the glands of the short tentacles on the disc indirectly 
excite movement of the exterior tentacles, for the stimulus 
of the glands of the disc acts on the bending part of the 
latter tentacles, near their bases, and does not first travel up 
the pedicels to the glands, to be then reflected back to the 
bending place. Some influence, however, does travel up to 
the glands, causing them to secrete most copiously, and the 
secretion to become acid, just such an influence as that 
which in animals is transmitted along the nerves to glands, 
modifying their power of secretion, independently of the 
condition of the blood-vessels. Over organic substances 
that yield soluble matter the tentacles remain clasped for a 
much longer time than over those not acted upon by the 
secretion, or over inorganic objects. That they have the 
power of rendering organic substances soluble, that is, that 
they have the power of digestion, is no longer a question 
of dispute. They certainly have this power, acting on 
