CHAPTER I 



INTRODUCTION 



THE word Zoology (Gr. woi/, an animal; Xoyos, a discourse) 



denotes the science which concerns itself with animals, 



endeavouring to find out what they are and how they 



came into being. It is a branch of the wider science of Biology 



(Gr. /3io9, life, Ao'yos, a discourse) ', which deals with all living things, 



plants as well as animals. Before any progress can be made with 



the study of Zoology, it is necessary to get clear ideas on two points: 



firstly, as to what is meant by life and living things; and secondly, 



as to how an animal is to be distinguished from a plant. 



The idea implied in calling a thing living, is that in some 

 respects its existence is similar to our own. Our own existence is 

 the only thing immediately known to us, the standard with which 

 we compare everything else. Every material object has certain 

 points of resemblance to our bodies, inasmuch as all are composed 

 of matter obeying the same laws of chemical affinity, gravitation, 

 and so forth ; it is necessary therefore to define the amount of re- 

 semblance which constitutes life. Now everyone knows that human 

 beings grow, that is, increase in size at the expense of matter called 

 food, which is different from themselves and that further, they give 

 rise at intervals to fresh human beings. These two fundamental 

 characteristics the power of growth and of multiplication define 

 life ; everything that can increase its bulk by building up foreign 

 matter into itself and that reproduces its like is said to be alive. 



The idea originally underlying the word animal was a self- 

 moving object as distinguished from a plant which was regarded 

 as motionless 2 and this distinction, is broadly speaking true. 



1 This term is too well established to admit of alteration but it implies a 

 mistranslation of /Jt'os. This does not mean 'life' in the physiological sense but 

 a period of life, a career, a life-time or circumstances of life, environment. 



2 It is true that to all general statements of Zoology, as to this, exceptions 

 could be found. The rule followed in this book is to have regard only to the 



S. & M. 1 



