1.4. 15 



whose attributes are not identical but analogous are separated. 

 For instance bird differs from bird by gradation, or by excess 

 and defect ; some birds have long feathers, others short ones, 

 but all are feathered. Bird and Fish are more remote and only 

 agree in having analogous organs ; for what in the bird is 

 feather, in the fish is scale. Such analogies can scarcely how- 

 ever serve universally as indications for the formation of groups, 

 for almost all animals present analogies in their corresponding 

 parts. 



The individuals comprised within a species, such as Socrates 

 and Coriscus, are the real existences ; but inasmuch as these 

 individuals possess one common specific form, it will suffice to 

 state the universal attributes of the species, that is, the attributes 

 common to all its individuals, once for all, as otherwise there will 

 be endless reiteration, as has already been pointed out. 



But as regards the larger groups — such as Birds — which com- 

 prehend many species, there may be a question. For on the one 

 hand it may be urged that as the ultimate species represent the 

 real existences, it will be well, if practicable, to examine these 

 ultimate species separately, just as we examine the species Man 

 separately; to examine, that is, not the whole class Birds col- 

 lectively, but the Ostrich, the Crane, and the other indivisible 

 groups or species belonging to the class. 



On the other hand, however, this course would involve repeated 

 mention of the same attribute, as the same attribute is common 

 to many species, and so far would be irrational and tedious. 

 Perhaps, then, it will be best to treat generically the universal 

 attributes of the groups that have a common nature and contain 

 closely allied subordinate forms, whether they are groups recognised 

 by a true instinct of mankind, such as Birds and Fishes, or groups 

 not popularly known by a common appellation, but withal com- 

 posed of closely allied subordinate groups ; and only to deal 

 individually with the attributes of a single species, when such 

 species — man, for instance, and any other such, if such there be — 

 stands apart from others, and does not constitute with them a 

 larger natural group. 



It is generally similarity in the shape of particular organs, or of 



the whole body, that has determined the formation of the larger 



groups. It is in virtue of such a similarity that Birds, Fishes, 



Cephalopoda, and Testacea have been made to form each a 



644 b. 



