352 PRINCIPLKS OF CLASSIFICATION. 



CHAPTER I. 



OF THE PRINCIPLES OF CLASSIFICATION, 



685. Plants and animals — the members of the or";anic king- 

 doms of nature — exist as individuals (13), of definite kinds, each 

 endowed with the characteristic power of producing hke individuals 

 and so of continuing the succession. The diflerent sorts (1.) are re- 

 produced true to their essential characteristics from generation to 

 generation ; and (2.) they exhibit unequal and very various degrees 

 of resemblance or of dissimilarity among themselves. These simple 

 propositions lie at the foundation of all classification and system in 

 natural history. Upon the first rests the idea of species ; upon the 

 second that of genera, orders., and all groups higher than species. 



G86. Individuals. The idea of individuality is derived from man 

 and ordinary animals, and thence naturally extended to vegetables. 

 Individuals are beings, owing their existence and their characteris- 

 tics to similar antecedent beings, and composed of parts which 

 togetlier constitute an independent Avhole, indivisible except by mu- 

 tilation. Individuality is perfectly exemplified in all the higher and 

 most of the lower animals, which multiply by sexual propagation 

 only, and in which the off^jiring, or the ovum, early separates from 

 the parent ; but it is incomjdetely realized in those animals of the 

 lower grade which are propagated by buds or offshoots as Avell as 

 by ova, and where the offspring may remain more or less intimately 

 connected with the parent. Still more is this so in plants, which 

 in every grade are or may be propagated by buds or offshoots ; 

 w^hich in vegetation develop an indefinite number of similar parts ; 

 whicli produce branches like the parent plant, and capable either of 

 continuing to grow in connection with it, or of becoming independent 

 (232). The individual plant, therefore, is evidently not a sim^ile 

 and true individual in the proper sense of the word, — in the sense 

 that an ordinary animal is. A kind of social or corporate individu- 

 ality in the complex radiated animals often gives a certain limita- 

 tion and shape to the congeries or polypidom, and in many of them 

 even subordinates certain parts to the common whole, assigning to 

 them special functions for the common weal : and this is universally 

 and more strikingly the case with plants, except the very simplest. 



