Classification . 1947 



attempt to classify, it should merely be a temporary arrangement, 

 made to answer some immediate purpose he may have in view. 



To revert, however, to the subject of the circular and quinary sys- 

 tem, it is impossible not to admire the very great ingenuity of the ar- 

 guments by which it was supported ; but even these, unless it had 

 possessed some foundation in reality, could not have obtained for it 

 the very extensive adoption that it was its lot to meet. Nature, al- 

 though her lines of separation are seldom clearly marked, certainly 

 does show types of organization in that unity of plan which charac- 

 terizes her works throughout, and also subordinate types, the species 

 included in these showing a still closer kind of affinity, in some cases 

 so distinctly marked that we doubt not for an instant where to fix 

 their limits ; while in the frequent cases of adaptation to the same 

 functions of species, or even groups of species, which have less real 

 affinity with each other than some of them may have with others fitted 

 for different purposes, " analogies " are by no means imaginary. It is, 

 however, not only far from being always the case that the limits of the 

 natural groups are clearly marked, but, so far from Nature pointing 

 out any particular number of subordinate groups necessary to consti- 

 tute one of the next degree, the limits of the various degrees of affinity 

 are themselves of our own establishing. We apply the terms, class, 

 order, family, &c, to indicate degrees of affinity closer or more re- 

 mote ; but the instances are few where Nature has so fixed the amount 

 of difference that we can no longer doubt as to how much is necessary 

 to constitute a distinct class, still less an order ; indeed the more we 

 descend into the details, the more difficult it is to draw the lines. 

 Naturalists are by no means agreed as to what should be the limits of 

 a genus : this name has been daily made more and more restricted in 

 its application since the time when classification had its origin, many 

 naturalists even constituting genera on distinctions so minute and tri- 

 fling, that, so far from aiding the progress of the science, they are but 

 an increasing burden on the memory. Again, how difficult it is to 

 settle what amount of difference is too little, or what too much, to 

 constitute a family ; and even where it has by general consent been 

 fixed, it sometimes happens, where the families are numerous, and 

 do not form among themselves groups which differ widely enough to 

 rank as orders, that they must be arranged in groups of intermediate 

 value, to which the name " tribes " has generally been applied. Sub- 

 classes, sub-orders, sub-families, sub-genera, are all among the attempts 

 made to accommodate Nature to the definitive order of our own divisions. 



Perhaps the mention of a few easily recognizable instances may 



