16 PERIOD I. 



swims ; that the snake comes nearer in all essentials to 

 the four-footed lizard, and even to the beast of the field, 

 than to the creeping earthworm. At a much later time 

 they discovered that pod-bearing or rose-like herbs 

 may resemble pod-bearing or rose-like trees more 

 closely than all trees resemble each other. Moreover, 

 a multitude of animals became known which cannot be 

 classed as either beasts, birds, fishes, or reptiles, and a 

 multitude of plants which cannot be classed as either 

 trees or herbs. 



Aristotle found himself obliged to rectify the tra- 

 ditional classification of animals in order to remove 

 gross anomalies. When learning decayed the traditional 

 classification came back. Thus the Ortus Sanitatis 

 (first published in 1475, and often reprinted) adopts 

 the division into (i) animals and things which creep 

 on the earth ; (2) birds and things which fly ; (3) 

 fishes and things which swim. No consistent 

 primary division of plants was proposed by Greek or 

 Roman, nor by anyone else until the seventeenth 

 century A.D. 



This conflict of systems should have raised questions 

 concerning the nature of classification and the relative 

 value of characters. Some of the most striking resem- 

 blances found among animals and plants are only 

 superficial ; others, though far less obvious, are funda- 

 mental. Whence this difference? Why should scientific 

 zoology make so little of the place of abode and the 

 mode of locomotion ; so much of the mode of 

 reproduction and the nature of the skeleton ? The 

 answers were vague, and even the questions were rare 

 and indistinct. But a metaphorical term came into 

 use which was henceforth more and more definitely 

 associated with fundamental, as distinguished from 



