protoplasm aggregating themselves in the purple fluid; these rapidly
increased in size, both within the cells of the glands and of the upper
ends of the pedicels. Particles of glass, cork, and cinders were also
placed on the glands of many tentacles; in 1 hr. several of them were
inflected, but after 1 hr. 35 m. there was no aggregation. Other
tentacles with these particles were examined after 8 hrs., and [page
43] now all their cells had undergone aggregation; so had the cells of
the exterior tentacles which had become inflected through the
irritation transmitted from the glands of the disc, on which the
transported particles rested. This was likewise the case with the short
tentacles round the margins of the disc, which had not as yet become
inflected. This latter fact shows that the process of aggregation is
independent of the inflection of the tentacles, of which indeed we have
other and abundant evidence. Again, the exterior tentacles on three
leaves were carefully examined, and found to contain only homogeneous
purple fluid; little bits of thread were then placed on the glands of
three of them, and after 22 hrs. the purple fluid in their cells almost
down to their bases was aggregated into innumerable, spherical,
elongated, or filamentous masses of protoplasm. The bits of thread had
been carried some time previously to the central disc, and this had
caused all the other tentacles to become somewhat inflected; and their
cells had likewise undergone aggregation, which however, it should be
observed, had not as yet extended down to their bases, but was confined
to the cells close beneath the glands.
Not only do repeated touches on the glands* and the contact of minute
particles cause aggregation, but if glands, without being themselves
injured, are cut off from the summits of the pedicels, this induces a
moderate amount of aggregation in the headless tentacles, after they
have become inflected. On the other hand, if glands are suddenly
crushed between pincers, as was tried in six cases, the tentacles seem
paralysed by so great a shock, for they neither become inflected nor
exhibit any signs of aggregation.
Carbonate of Ammonia. Of all the causes inducing aggregation, that
which, as far as I have seen, acts the quickest, and is the most
powerful, is a solution of carbonate of ammonia. Whatever its strength
may be, the glands are always affected first, and soon become quite
opaque, so as to appear black. For instance, I placed a leaf in a few
drops of a strong solution, namely, of one part to 146 of water (or 3
37