380 HISTORY OF ZOOLOGY. 



Aristotle's nine Books On Animals are a work 

 enumerating the differences of animals in almost all 

 conceivable respects; in the organs of sense, of 

 motion, of nutrition, the interior anatomy, the exte- 

 rior covering, the manner of life, growth, generation, 

 and many other circumstances. These differences 

 are very philosophically estimated. "The corre- 

 sponding parts of animals," he says 1 , "besides the 

 differences of quality and circumstance, differ in 

 being more or fewer, greater or smaller, and, speak- 

 ing generally, in excess and defect. Thus some 

 animals have crustaceous coverings, others hard 

 shells; some have long beaks, some short; some 

 have many wings, some have few. Some again have 

 parts which others want, as crests and spurs." He 

 then makes the following important remark : "Some 

 animals have parts which correspond to those of 

 others, not as being the same in species, nor by 

 excess and defect, but by analogy ; thus a claw is 

 analogous to a thorn, and a nail to a hoof, and a 

 hand to the nipper of a lobster, and a feather to a 

 scale ; for what a feather is in a bird, that is a scale 

 in a fish." 



It will not, however, be necessary, in order to 

 understand Aristotle for our present purpose, that 

 we should discuss his notion of analogy. He pro- 

 ceeds to state his object 2 , which is, as we have said, 

 to describe the differences of animals in their struc- 

 ture and habits. He then observes, that for struc- 



1 Lib. i. c. i. 2 c. ii. 



