Crup. XI. GENERAL SUMMARY. 277 
be called a reflex action, though probably very dif- 
ferent from that proceeding from the nerve-ganglion 
of an animal; and it is the only known case of reflex 
action in the vegetable kingdom. 
About the mechanism of the movements and the 
nature of the motor impulse we know very little. 
During the act of inflection fluid certainly travels from 
one part to another of the tentacles. But the hypo- 
thesis which agrees best with the observed facts is 
that the motor impulse is allied in nature to the 
aggregating process; and that this causes the mole- 
cules of the cell-walls to approach each other, in the 
same manner as do the molecules of the protoplasm 
within the cells; so that the cell-walls contract. But 
some strong objections*may be urged against this view. 
The re-expansion of the tentacles is largely due to 
the elasticity of their outer cells, which comes into 
play as soon as those on the inner side cease con- 
tracting with prepotent force; but we have reason to 
suspect that fluid is continually and slowly attracted 
into the outer cells during the act of re-expansion, 
thus increasing their tension. 
I have now given a brief recapitulation of the chief 
points observed by me, with respect to the struc- 
ture, movements, constitution, and habits of Drosera 
rotundifolia ; and we see how little has been made out 
in comparison with what remains unexplained and 
unknown. : 
