Divisions of Life and Time 



would natiu^ally group tbem according to their 

 subjects — histories in one place, novels in an- 

 other, books of travel in still another. And 

 just as books are arranged by their subjects or 

 contents, and not by theii' bindings, so animals 

 are classified according to their contents or 

 structure, and not by their coverings, form, or 

 external appearance. If in the present brief 

 review of the animal kingdom more attention 

 seems to be paid to mere appearance than to 

 those plans of structure by which animals are 

 grouped, it is because to the great majority of 

 people appearance is not only the more interest- 

 ing but very much the more familiar. Very 

 few care to trouble themselves wdth the plan 

 on which a creature is built any more than 

 they would care for the plans of a pretty cot- 

 tage ; the completed structure is the thing of 

 interest. But the paleontologist, the delver 

 into the ruins of the past, rarely has more than 

 the framework to deal with, and counts himself 

 as extremely fortunate if the greater part even 

 of this be not missing. So the reader will 

 please take it for granted that the various as- 



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