INTRODUCTION. ,% 
into the two sciences of Boftazy, which treats of plants, and 
Zoology (Gr. zoén, animal; logos, discourse), which treats. of 
animals. The term Natural History, again, is generally under- 
stood nowadays as being equivalent to Zoology alone, though 
originally it was applied to the study of all natural objects in- 
discriminately. | 
2, DIFFERENCES BETWEEN ANIMALS AND PLANTS. 
It now becomes necessary to inquire into the differences 
which subsist between animals and plants, and which enable 
us to separate the kindred sciences of Zoology and Botany. It 
might have been thought that nothing could be easier than to 
determine the animal or vegetable nature of any given organism ; 
and such, indeed, was the almost universal belief of older ob- 
servers. In point of fact, however, no hard-and-fast line can be 
drawn, in the present state of our knowledge, between the ani- 
mal and vegetable kingdoms, and it is often a matter of extreme 
difficulty, or even wholly impossible, to decide positively whe- 
ther we are dealing with an animal ora plant. So deeply has 
this difficulty been felt of late, that a most able zoologist—Dr 
Ernst Haeckel—has proposed to form an intermediate kingdom, 
which he calls the Regnum Protisticum, and in which he pro- 
poses to place all organisms of a doubtful character. Even such 
a cautious observer as Professor Rolleston, whilst questioning 
the propriety of this step, is forced to come to.the conclusion 
that “there are organisms which at one period of their life ex- 
hibit an aggregate of phenomena such as to justify us in speak- 
ing of them as animals, whilst at another they appear to be as 
distinctly vegetable.” In the case of the higher members of the 
two kingdoms there is no difficulty in arriving at a decision. 
The higher animals are readily separated from the higher plants 
by the possession of a distinct nervous system, of locomotive 
power which can be voluntarily exercised, and of an internal 
cavity fitted for the reception and digestion of solid food. The 
higher plants, on the other hand, possess no nervous system or 
organs of sense, are incapable of voluntary changes of place, 
and are not.provided with any definite internal cavity, their 
food being wholly fluid or gaseous. 
The lower animals (Protozoa) cannot, however, be separated in many 
cases from the lower plants (Protophyta) by these distinctions, since 
many of the former have no digestive cavity, and are destitute of a ner- 
