118 



Zoology in its widest sense may aim at a full and complete 

 knowledge of animal life, from the simple cell of the lowest protozoon to 

 that of the most complex or differentiated structure in existence. It 

 may not only be a knowledge of animal life as it now exists, with its 

 almost infinite number of variations and complexities, but it may extend 

 its researches away back for countless ages and inquire into their origin 

 or beginning — inquire from whence they came and whither* they are 

 tending. Truly a vast subject. 



In the ordinary study of animal life the various kinds are grouped 

 together in a certain order. The number of the different sorts of 

 animals being very great — much greater than that of plants — and the 

 diversity among them also being greater, a division of the same into 

 branches relating to different groups may naturally take place, as 

 without an arrangement of this kind it would be almost impossible to 

 describe an animal in such a way as to enable the student to find very 

 readily any particular animal described. This me'hod of grouping 

 animals together is somewhat as follows : Supposing we take up that 

 branch of zoology which has for its subject bird life, or ornithology — 

 (ornis a bird, logos a discourse). The first step in classification would 

 be to ascertain some peculiarity common to all animals which go by the 

 name of bird. It would occur to most of us at once that all birds have 

 feathers, and that no other animal is similarly clothed. This one char- 

 acteristic would be sufficient to determine a bird's place among animals. 

 Having got this far, it would very soon be perceived that structural 

 differences, particularly in the feet, existed among birds, some having 

 three toes, some four, som^ with three in front and one behind, some 

 with two in front and two behind, others again with three in front 

 only, some with their toes joined together with a thin skinny web, and 

 several other points of difference. It would be quite natural to begin 

 classification by grouping together all the birds having the same kind of 

 feet. We would not think of placing a bird with feet adapted for 

 perching in the same group with those with feet adapted for swimming. 

 We would soon have several large orders of birds arranged by their 

 feet peculiarities ; but this grouping would not be sufficiently definite, 

 as many birds with feet somewhac alike are very different in other 

 respects; so that in order to designate any particular bird with certainty 



