CHAPTER XXVII. 



Pisces (Fishes). 



In passing from one country to another, we do not find 

 any boundary lines in nature corresponding to those which 

 we see upon our maps. There may be a gradual change 

 of features, indeed ; as the vegetation that characterises 

 Spain differs from that of France, and this latter from 

 that of Prussia j but the traveller is not conscious of any 

 abrupt change, the last mile of his journey on one side 

 of either frontier being pretty much the same as the first 

 mile beyond it. We speak, too, of the various ranks and 

 classes of society : the labourer, the artisan, the trades- 

 man, the manufacturer, the merchant, the professional 

 man, the scientific man, the statesman, the peer, the 

 prince, the sovereign ; but the homes, the raiment, the 

 manners of these, though characterised by well-marked 

 diversities and peculiarities, are not separated by broad 

 lines of demarcation, but pass imperceptibly into each 

 other. The diversities exist in nature, but the boundary 

 Hues are arbitrary. 



So it is in Natural History. The student will do well 

 to bear in mind continually that those subdivisions of 

 organic beings which we call Classes, Orders, Families, 

 and Genera, are but convenient aids for recording and re- 



