363 POPULAR SCIENCE REVIEW. 
SPONTANEOUS MOVEMENTS IN PLANTS. 
By ALFRED W. BENNETT, M.A., B.Sc., F.L.S. 
[PLATE LXXXIX.] 
T HAT there are no “hard and fast lines ” in Nature is a truth 
which is more and more forcing' itself upon the minds of 
men of science. The older naturalists delighted to circum- 
scribe their own special domains within sharply-marked boun- 
daries, which no trespassers were allowed to pass. We have 
long given up the attempt thus accurately to map out the 
kingdom of Nature. Her varied productions are connected 
with one another by innumerable links and cross-links ; and 
our systems of classification, even the most “ natural,” are but 
an imperfect human contrivance for bringing together those 
forms which present the most evident marks of resemblance 
or affinity. While the truth of this law is most familiar in 
the case of those smaller subdivisions of the animal and 
vegetable kingdoms — classes, orders, and genera — which are 
connected with one another by innumerable intermediate forms, 
it is none the less certain in the line of demarcation which 
separates these two great kingdoms themselves from one another. 
In attempting to draw up a definition which shall serve accu- 
rately and infallibly to distinguish between the Animal and 
Vegetable Kingdoms, we find ourselves compelled to abandon 
one supposed crucial test after another, and to content ourselves 
at last with framing, as in the case of the lower subdivisions, 
an assemblage of characters, by the tout ensemble of which we 
must decide whether our organism is an animal or a plant. So 
great is the uncertainty as to the actual boundary-line, that large 
groups of lowly organisms, such as those known as Diatoms and 
Desmidese, have been regarded by experienced authorities as 
belonging to each kingdom ; and one of the ablest of living 
naturalists, Ernst Haeckel’ of Jena, has proposed the division of 
the material universe not into three but into four kingdoms — 
animals, plants, protista, and minerals, the new kingdom of 
Protista including the most lowly organised forms of what are 
generally considered animals and plants, from the Flagellate 
