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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. 



IT 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 

 invention : they form no part of Nature ; Linnaeus 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 Algae, 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 Algae, 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 



