AI4 JOURNAL OF SCIENCE. 
genus to which it belongs have a peculiar interest to the botanist, 
because they have developed a number of their leaves into singular 
little bladders. If we consider first a European species—U. vulgaris 
—we find that the great de Candolle gives the following as his 
explanation of the occurrence of the bladders :—‘ These bladders are 
rounded and furnished with a kind of moveable operculum ; in the 
young plant they are filled with a mucus heavier than water, and the 
plant, submerged by this ballast, remains at the bottom: Towards 
the flowering season the leaves secrete a gas which enters the 
bladders, raises the operculum and drives out the mucus, when the 
plant now furnished with aerial bladders rises slowly, floats on the 
surface and there flowers. This accomplished, the leaves again 
secrete mucus, which replaces the air in the bladders, and the plant 
redescends to the bottom and ripens its seeds in the place where they 
are to be sown.” 
When we investigate the origin of the bladders themselves we 
are brought face to face with avery curious problem, one in fact 
which is far more difficult to follow than the origin of the subsequent 
modifications. Perhaps de Candolle’s explanation is correct, as. 
pointing out the primary function of the bladders, but it does not 
follow that he is right at all. An allied genus Pinguwicula, or butter- 
worts, has no submerged leaves, yet all the species appear to have 
acquired the carnivorous properties for which UV¢ricularia is noted. 
De Candolle does not seem to have noticed that in all the species of 
Utricularia, the bladders usually contain small aquatic animals, nor to 
have seen that in the majority of species the function of floating up 
the plant has been almost or totally lost, while that of catching animal 
prey has become greatly perfected. Thus if welook into the structure 
of a bladder of U. neglecta, as described by Darwin, we find that it is 
produced into two long prolongations, each bearing six or seven long 
bristles, and under these is the entrance to the bladder, covered by a 
curious valve. This valve only opens inwards, so that anything small 
enough can easily force its way into the bladder, but once inside, 
it cannot get out. The internal surface of the bladder is covered 
with little four-armed processes, which have been proved to 
possess the power of absorbing nitrogenous materials, such as 
would result from the decay of the bodies of animals. The 
only New Zealand species which I have examined—U. monanthos 
—has no valve, but the entrance inwards is very clearly marked by 
two flanged processes, while apparently the way out is not so easily 
found. Probably also the water inside is supercharged with carbonic 
acid, for the animals which get in appear soon to be suffocated. 
Those plants examined by me contained mostly small crustacea, from 
one to ten individuals being present in a bladder. Seeing that 
apparently no attractive structures exist in the bladders to entice 
crustacea to them, it may be asked, why should they enter at all? 
It is probably due to the fact, familiar to every one who has studied 
these animals, that most small aquatic animals, and particularly those 
furnished with hard shells, habitually try to enter every small crevice 
in search of food. In this case, their curiosity, like that of Blue- 
beard’s wives, proves fatal to them. Very recently (‘‘ Nature,’ Vol. 
XXX., p. 295), Mr. G. E. Simms, junr., has shown that the bladders 
of U. vulgaris not only prey upon flies, larve, worms, crustacea, and 
