fm 
Cuar. XE] GENERAL SUMMARY. 219 
exterior tentacles down their pedicels. The exciting 
influence, therefore, which is transmitted from one part of 
the leaf to another must be different from that which 
actually induces aggregation. The process does not depend 
on the glands secreting more copiously than they did before ; 
and is independent of the inflection of the tentacles. It 
continues as long as the tentacles remain inflected, and as 
soon as these are fully re-expanded, the little masses of 
protoplasm are all redissolved; the cells becoming filled with 
homogeneous purple fluid, as they were before the leaf was 
excited. 
As the process of aggregation can be excited by a few 
touches, or by the pressure of insoluble particles, it is 
evidently independent of the absorption of any matter, and 
must be of a molecular nature. Even when caused by the 
absorption of the carbonate or other salt of ammonia, or an 
infusion of meat, the process seems to be of exactly the same 
nature. The protoplasmic fluid must, therefore, be in a 
singularly unstable condition, to be acted on by such slight 
and varied causes. Physiologists believe that when a nerve 
is touched, and it transmits an influence to other parts of the 
nervous system, a molecular change is induced in it, though 
not visible to us. Thereforeit is a very interesting spectacle 
to watch the effects on the cells of a gland, of the pressure of 
a bit of hair, weighing only +455 of a grain and largely 
supported by the dense secretion, for this excessively slight 
pressure soon causes a visible change in the protoplasm, 
which change is transmitted down the whole length of the 
tentacle, giving it at last a mottled appearance, distinguish- 
able even by the naked eye. 
In the fourth chapter it was shown that leaves placed for 
a short time in water at a temperature of 110° Fahr. (438°°3 
Cent.) become somewhat inflected; they are thus also 
rendered more sensitive to the action of meat than they 
were before. If exposed to a temperature of between 115° 
and 125° (46° -1—51°-6 Cent.), they are quickly inflected, and 
their protoplasm undergoes aggregation; when afterwards 
placed in cold water, they re-expand. Exposed to 130° (54°°4 
Cent.), no inflection immediately occurs, but the leaves are 
only temporarily paralysed, for on being left in cold water, 
they often become inflected and afterwards re-expand. In 
one leaf thus treated, I distinctly saw the protoplasm in 
movement. In other leaves treated in the same manner, and 
