Cuar. X.] DIRECTION OF INFLECTED TENTACLES. 197 
bending of the tentacles, as we clearly see when leaves are 
immersed in certain strong solutions. Nor does it depend on 
increased secretion from the glands, and this is shown by 
several facts, more especially by the papillae, which do not 
secrete, yet undergoing aggregation, if given carbonate of am- 
monia or an infusion of raw meat. When a gland is directly 
stimulated in any way, as by the pressure of a minute par- 
ticle of glass, the protoplasm within the cells of the gland 
first becomes aggregated, then that in the cells immediately 
beneath the gland, and so lower and lower down the tentacles 
to their bases ;—that is, if the stimulus has been sufficient 
and not injurious. Now, when the glands of the disc are 
excited, the exterior tentacles are affected in exactly the same 
manner: the aggregation always commences in their glands, 
though these have not been directly excited, but have only 
received some influence from the disc, as shown by their 
increased acid secretion. The protoplasm within the cells 
immediately beneath the glands are next affected, and so 
downwards from cell to cell to the bases of the tentacles. 
This process apparently deserves to be called a reflex action, 
in the same manner as when a sensory nerve is irritated, and 
carries an impression to a ganglion which sends back some 
influence to a muscle or gland, causing movement or increased 
secretion; but the action in the two cases is probably of a 
widely different nature. After the protoplasm in a tentacle 
has been aggregated, its redissolution always begins in the 
lower part, and slowly travels up the pedicel to the gland, so 
that the protoplasm last aggregated is first redissolved. 
This probably depends merely on the protoplasm being less 
and less aggregated, lower and lower down in the tentacles, 
as can be seen plainly when the excitement has been slight. 
As soon, therefore, as the aggregating action altogether 
ceases, redissolution naturally commences in the less strongly 
aggregated matter in the lowest part of the tentacle, and is 
there first completed. : 
Direction of the Inflected Tentacles—When a particle of 
any kind is placed on the gland of one of the outer tentacles, 
this invariably moves towards the centre of the leaf; and so 
it is with all the tentacles of a leaf immersed in any exciting 
fluid. The glands of the exterior tentacles then form a ring 
round the middle part of the disc, as shown in a previous 
figure (fig. 4, p. 9). The short tentacles within this ring 
still retain their vertical position, as they likewise do when 
