Cuar. Ul THE PROCESS OF AGGREGATION. 55 
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 pheno- 
mena 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 in- 
organic 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 
transmitted 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 aggrega- 
tion 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 
5 
