mind what I have witnessed when a small snake makes a large frog its
victim. But as the valve does not appear to be in the least irritable,
the slow swallowing process must be the effect of the onward movement
of the larva.
It is difficult to conjecture what can attract so many creatures,
animal- and vegetable-feeding crustaceans, worms, tardigrades, and
various larv , to enter the bladders. Mrs. Treat says that the larv
just referred to are vegetable-feeders, and seem to have a special
liking for the long bristles round the valve, but this taste will not
account for the entrance of animal-feeding crustaceans. Perhaps small
aquatic animals habitually try to enter every small crevice, like that
between the valve and collar, in search of food or protection. It is
not probable that the remarkable transparency of the valve is an
accidental circumstance, and the spot of light thus formed may serve as
a guide. The long bristles round the entrance apparently serve for the
same purpose. I believe that this is the case, because the bladders of
some epiphytic and marsh species of Utricularia which live embedded
either in entangled vegetation or in mud, have no bristles round the
entrance, and these under such conditions would be of no service as a
guide. Nevertheless, with these epiphytic and marsh species, two pairs
of bristles project from the surface of the valve, as in the aquatic
species; and their use probably is to prevent too large animals from
trying to force an entrance into the bladder, thus rupturing orifice.
As under favourable circumstances most of the bladders succeed in
securing prey, in one case as many as ten crustaceans; as the valve is
so well fitted to [page 410] allow animals to enter and to prevent
their escape; and as the inside of the bladder presents so singular a
structure, clothed with innumerable quadrifid and bifid processes, it
is impossible to doubt that the plant has been specially adapted for
securing prey. From the analogy of Pinguicula, belonging to the same
family, I naturally expected that the bladders would have digested
their prey; but this is not the case, and there are no glands fitted
for secreting the proper fluid. Nevertheless, in order to test their
power of digestion, minute fragments of roast meat, three small cubes
of albumen, and three of cartilage, were pushed through the orifice
into the bladders of vigorous plants. They were left from one day to
350