REVIEWS. 
405 
has performed many experiments on the subject, and has inquired into the 
mode in which a stimulant is made to travel, yet we do not think he has 
added very much to our knowledge on the subject. His (or rather his 
son’s) drawing, which represents a leaf of Drosera with its tentacles in- 
folded over a piece of meat, is an admirable illustration. It shows the 
whole process so much better than words can convey it, and to our minds it 
is exceedingly like a sea-anemone that had just grasped a small crustacean. 
Well might the author say, “We might imagine that we were looking at a 
lowly organised animal seizing prey with its arms,” and, further on, that 
“ the case of the Drosera is far more interesting [than the motion of ten- 
drils], as here the tentacles are not directly excited, but receive an impulse 
from a distant point ; nevertheless , they bend accurately towards this point.” 
With regard to this very interesting process, the following attempted ex- 
planation is offered by Mr. Darwin : — “ About the mechanism of the move- 
ments and the nature of the motive impulse we know very little. During 
the act of inflation fluid certainly travels from one part to another of the 
tentacles. But the hypothesis which agrees best with the observed facts 
is, that the motive impulse is allied in nature to the aggregating process, 
and that this causes the molecules 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 objections may be urged against 
this view.” After some further remarks the author truly says, “ We see 
how little has been made out in comparison with what remains unexplored 
and unknown.” 
Mr. Darwin describes with the utmost minuteness his numerous experi- 
ments on some of these animal feeders, and it is perfectly astonishing to see 
the number of flies which a single specimen of some of the plants observed 
by him have captured. And the reader must not suppose that they are 
simply captured insects. They are regularly digested. The plant closes on 
them, and they are thus killed ; and it is not till the whole of their soft 
parts have been dissolved and absorbed that they open, and thus reject the 
excrementitious matter. Thus it is that certain of these plants are pro- 
vided with such imperfect roots ; they do not require food supplied through 
the roots, because they are able to obtain a quantity through the multitude 
of insects they captivate. “ There can hardly be a doubt,” says the author, 
that these plants “ have the power of dissolving animal matter by the aid of 
their secretion, which contains an acid, together with a ferment almost iden- 
tical in nature with pepsin ; and that they afterwards absorb the matter 
thus digested. This is certainly the case with Drosera, Drosophyllum, and 
Dioncea ; almost certainly with Aldrovanda , and, from analogy, very pro- 
bably with JRoridula and JByblis. We can thus understand why it is that 
the three first-named genera are provided with such small roots, and that 
Aldrovanda is quite rootless ; about the roots of the two other genera nothing 
is known. It is no doubt a surprising fact that a whole group of plants 
should subsist partly by digesting animal matter, and partly by decomposing 
carbonic acid.” But Mr. Darwin instances as remarkable a fact in the Animal 
Kingdom by pointing to those peculiar rhizocephalous crustaceans which 
are absolutely destitute of an alimentary canal. 
W e cannot touch on any of the author’s observations on the genus 
