188 THE DESCENT OF MAN. Part I. 



. inals as are these two latter groups conjoined. This 

 view has not been accepted, as far as I am aware, by 

 any naturalist capable of forming an independent judg- 

 ment, and therefore need not here be further con- 

 sidered. 



We can understand why a classification founded on 

 any single character or organ — even an organ so won- 

 derfully complex and important as the brain — -or on the 

 high development of the mental faculties, is almost sure 

 to prove unsatisfactory. This principle has indeed been 

 tried with hymenopterous insects; but when thus classed 

 by their habits or instincts, the arrangement proved 

 thoroughly artificial. 3 Classifications may, of course, be 

 based on any character whatever, as on size, colour, or 

 the element inhabited ; but naturalists have long felt a 

 profound conviction that there is a natural system. This 

 system, it is now generally admitted, must be, as far 

 as possible, genealcgical in arrangement, — that is, the 

 co-descendants of the same form must be kept together 

 in one group, separate from the co-descendants of any 

 other form ; but if the parent-forms are related, so will 

 be their descendants, and the two groups together will 

 form a larger group. The amount of difference between 

 the several groups — that is the amount of modification 

 which each has undergone — will be expressed by such 

 terms as genera, families, orders, and classes. As we 

 have no record of the lines of descent, these lines can 

 be discovered only by observing the degrees of re- 

 semblance between the beings which are to be classed. 

 For this object numerous points of resemblance are of 

 much more importance than the amount of similarity 

 or dissimilarity in a few points. If two languages 

 were found to resemble each other in a multitude of 



3 Westwood, ' Modern Class, of Insects,' vol. ii. 1840, p. S7. 



