Butterwort 275 
Near the base of the leaf there are one or more 
little bladders, bearing a singular likeness to some 
of the freshwater crustaceans popularly known as 
Water-fleas—a resemblance largely due to the pre- 
sence of two bristle-bearing appendages at the end 
farthest from the foot-stalk. The bladders are trans- 
lucent and pale-green, and they vary in size, in the 
different species, from one-twelfth to a quarter of 
an inch across. Between the appendages—to which 
Darwin gave the name of antenne—and the foot-stalk 
on the lower surface there is an opening closed by 
a valve, and on each side of the opening there are 
four long bristles. These, together with those borne 
by the antennze, form a kind of net, whose function 
~ appears to be to check the onward progress of small 
creatures and induce them to pass into the bladder, 
which they do by pressure against the valve. This 
valve is a clear, colourless, elastic plate, whose free 
margin moves inwards in order to open the entrance 
and admit the low forms of life that are ever pushing 
in. Its inner face is covered with glandular processes, 
which appear to absorb but not to secrete. There is 
apparently no digestive process as in Butterwort, 
the entrapped victims being killed by lack of oxygen, 
and retained until decomposition has rendered them 
capable of being absorbed. 
About thirty years ago Mr. Holland remarked to 
the High Wycombe Natural History Society that 
“water insects are often found imprisoned in the 
bladders,” and suggested that their bodies were 
“destined for the plant to feed on.” It was at 
least partially due to this observation that Mr. Darwin 
was induced to experiment with the plant, to which 
18 
