INTRODUCTION AND GENERAL 

 CLASSIFICATION 



ZOOLOGY (Gr. zoon, animal ; logos, discourse) is the study of 

 animal life, as distinguished from Botany (Gr. botane, a herb), 

 the study of plant life, the two together forming the science 

 of living organisms known as Biology. 



It is well to bear in mind from the first that these two 

 branches of the tree of life, though bearing such markedly 

 different forms at their apices, unite at their base ; the animal 

 and plant characteristics become merged together, so that 

 in the simplest forms it is often difficult, if not impossible, to 

 distinguish with certainty as plant or animal, the little speck 

 of living matter which constitutes the whole organism. 



General ^ we consider all the members of the animal 



Classification, kingdom known to us, the great variety of them 

 Nomenclature. i s remarkable, and, at the same time, no less 

 remarkable is the fact, that when we come to examine their 

 structure closely we find they can be grouped in quite a small 

 number of primary groups, with a peculiar type of structure 

 characteristic of each ; these primary groups of animals are 

 known as Phyla or sub-kingdoms. Most of these phyla con- 

 tain an enormous number of forms, which, though having 

 certain underlying characters in common, in many ways dis- 

 play great variety, and so we subdivide each phylum into 

 Classes, the members of each class being alike in certain 

 secondary characteristics which distinguish them from the 

 other classes of the same phylum. 



Similarly we divide each class into Orders, each order into 

 Families, each family into Genera, and finally each genus into 

 Species. The individuals included in one species will dis- 

 play only those slight variations which we are accustomed to 



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