Cnar. III] THE PROCESS OF AGGREGATION. 47 
fluid. The redissolution in these cases may, I presume, be attributed 
to endosmose. 
On the Proximate Causes of the Process of Aggregation. 
As most of the stimulants which cause the inflection of the 
tentacles likewise induce aggregation in the contents of their 
cells, this latter process might be thought to be the direct 
result of inflection ; but this is not the case. If leaves are 
placed in rather strong solutions of carbonate of ammonia, for 
instance of three or four, and even sometimes of only two 
grains to the ounce of water (i.e. one part to 109, or 146, or 
218, of water), the tentacles are paralysed, and do not become 
inflected, yet they soon exhibit strongly marked aggregation. 
Moreover, the short central tentacles of a leaf which has been 
immersed in a weak solution of any salt of ammonia, or in 
any nitrogenous organic fluid, do not become in the least 
inflected; nevertheless, they exhibit all the phenomena of 
aggregation. On the other hand, several acids cause strongly 
pronounced inflection, but no aggregation. 
It is an important fact that when an organic or inorganic 
object is placed on the glands of the disc, and the exterior 
tentacles are thus caused to bend inwards, not only is the 
secretion from the glands of the latter increased in quantity 
and rendered acid, but the contents of the cells of their 
pedicels become aggregated. The process always commences 
in the glands, although these have not as yet touched any 
object. Some force or influence must, therefore, be trans- 
mitted from the central glands to the exterior tentacles, first 
to near their bases causing this part to bend, and next to the 
glands causing them to secrete more copiously. After a 
short time the glands, thus indirectly excited, transmit or 
reflect some influence down their own pedicels, inducing 
aggregation in cell beneath cell to their bases. 
It seems at first sight a probable view that aggregation is 
due to the glands being excited to secrete more copiously, so 
that sufficient fluid is not left in their cells, and in the cells 
of the pedicels, to hold the protoplasm in solution. In favour 
of this view is the fact that aggregation follows the inflection 
of the tentacles, and during the movement the glands gener- 
ally, or, as I believe, always, secrete more copiously than 
they did before. Again, during the re-expansion of the 
tentacles, the glands secrete less freely, or quite cease to 
