Cuap. III.] THE PROCESS OF AGGREGATION. 37 
compressor. In 15 m.I distinctly saw extremely minute spheres of 
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 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 them- 
selves 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, isa 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 
grs. to 1 0z.), and observed it under a high power. All the glands 
began to darken in. 10s. (seconds); and in 13 s. were conspicuously 
* Judging from an account of M. _ beris, after they have been excited by 
Heckel’s observations, which I have a touch and have moved; for hesays, 
only just seen quoted in the ‘Gar- ‘the contents of each individual cell 
dener’s Chronicle’ (Oct. 10, 1874), he are collected togethcr in the centre 
appears to have observed a similar of the cavity.” 
phenomenon in the stamens of Ber- 
