SPONTANEOUS MOVEMENTS IN PLANTS. 2S1 



accurately to map out the kingdom of Nature. Her varied produc- 

 tions 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 innu- 

 merable 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 accurately 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 Desmidea?, 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 king- 

 doms animals, plants, protista, and minerals, the new kingdom of 

 Protista including the most lowly-organized forms of what are gener- 

 ally considered animals and plants, from the Flagellate Infusoria to 

 the Fungi, distinguished by the absence of sexes, and the mode of re- 

 production by gemmation or fission alone. The soundness of this new 

 classification is not, however, admitted by the best remaining authori- 

 ties in England or Germany. 



One of the most obvious distinctions between the Animal and 

 Vegetable Kingdoms consists in the possession by the former of a 

 power of voluntary motion of either the whole or a part of the body, 

 dependent on the presence of a distinct nervous system, which is ab- 

 sent in the latter ; a distinction obvious enough when contrasting any 

 of the higher forms of the two kingdoms, but which, like all other in- 

 dividual characters, fails when pressed to too rigid a test. There are 

 animals, so regarded by the best naturalists, and possessing other 

 characters which compel us to refer them to this class, whose power 

 of motion is confined to the " contractility " common to all protoplas- 

 mic substance, and which are absolutely devoid of a nervous system ; 

 and there are plants, unquestionable plants, which possess powers of 

 spontaneous motion strictly compai'able to those exhibited by the 

 lower animals. It may be interesting to collect together a few illus- 

 trations of this last-named fact, some of which appear to the writer 

 scarcely explicable by the application of any of those laws which 

 govern inert unorganized matter. 



