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CHAPTER IV. 
PROTOZOA. 
“Natura nusquam magis quam in minimis tota est.” 
“ Nature is nowhere more perfect than in her smaller works.”-—PLINy. 
Ir will not be out of place here to offer some remarks on the animal 
kingdom in general, as well as on the great divisions thereof which 
form the subject of this volume. But, considering the vastness of the 
subject, we must be indeed brief. The divisions, classes, orders, 
families, genera, and species, which naturalists have established in 
order to study and describe animals, are admirable contrivances for 
facilitating the study of creatures numerous as the sands of the sea- 
shore. Without this precious means of logical distribution, the 
individual mind would recoil before the task of describing the in- 
numerable groups of existing animal life. But the reader must never 
forget that these methodical divisions are, after all, due to human 
mvention : they form no part of Nature ; Linnzeus tells us that Nature 
makes no leaps—natura non facit saltus—she passes in a manner 
almost insensibly from one stage of organisation to another ; human 
systems but try to follow in her footsteps. 
When we come to examine the organisms which stand as it 
were on the confines of the animal and vegetable kingdoms, we 
realise how difficult it is to see the precise line of demarcation 
which separates these great kingdoms of Nature. We have seen 
in “The Vegetable World” germs of the simplest organisation, 
spores, as in the Algz, which seem to be invested with some of 
the characteristics of animal life, for they appear to be gifted with 
organs of locomotion, namely, vibratile cilia, by means of which they 
execute movements which are to all appearance quite voluntary. 
Side by side with these are the fecundating corpuscles, known as 
antherozoids among the Algze, Mosses, and Ferns, which seem to go 
and come like the inferior animals, seeking to penetrate into cavities, 
withdrawing themselves, returning again, and again introducing 
themselves, and exhibiting all the signs of an apparent effort. If we 
compare some of the early stages of the Protozoa with these moving 
