fluids, which seemed adapted for the purpose, would produce the same
effects on the processes as the absorption of decayed animal matter.
Such experiments are, however, troublesome; for it is not sufficient
merely to place a branch in the fluid, as the valve shuts so closely
that the fluid apparently does not enter soon, if at all. Even when
bristles were pushed into the orifices, they were in several cases
wrapped so closely round by the thin flexible edge of the valve that
the fluid was apparently excluded; so that the experiments tried in
this manner are doubtful and not worth giving. The best plan would have
been to puncture the bladders, but I did not think of this till too
late, excepting in a few cases. In all such trials, however, it cannot
be ascertained positively that the bladder, though translucent, does
not contain some minute animal in the last stage of decay. Therefore
most of my experiments were made by cutting bladders longitudinally
into two; the quadrifids were examined with No. 8 of Hartnack, then
irrigated, whilst under the covering glass, with a few drops of the
fluid under trial, kept in a damp chamber, and re-examined after stated
intervals of time with the same power as before.
[Four bladders were first tried as a control experiment, in the manner
just described, in a solution of one part of gum arabic to 218 of
water, and two bladders in a solution of one part of sugar to 437 of
water; and in neither case was any [page 414] change perceptible in the
quadrifids or bifids after 21 hrs. Four bladders were then treated in
the same manner with a solution of one part of nitrate of ammonia to
437 of water, and re-examined after 21 hrs. In two of these the
quadrifids now appeared full of very finely granular matter, and their
protoplasmic lining or primordial utricle was a little shrunk. In the
third bladder, the quadrifids included distinctly visible granules, and
the primordial utricle was a little shrunk after only 8 hrs. In the
fourth bladder the primordial utricle in most of the processes was here
and there thickened into little, irregular, yellowish specks; and from
the gradations which could be traced in this and other cases, these
specks appear to give rise to the larger free granules contained within
some of the processes. Other bladders, which, as far as could be
judged, had never caught any prey, were punctured and left in the same
solution for 17 hrs.; and their quadrifids now contained very fine
granular matter.
A bladder was bisected, examined, and irrigated with a solution of one
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