CLASSIFICATION. 409 



and there will be an immense number of forms finely 

 graduated in their resemblances. Exact and distinct 

 classification will then be almost impossible, and the 

 wisest course will be not to attempt arbitrarily to distin- 

 guish forms closely related in nature, but to allow that 

 there exist transitional forms of eveiy degree, to mark out 

 if possible the extreme limits of the family relationship, 

 and perhaps to select the most generalized form, or that 

 which presents the greatest number of close resemblances 

 to others of the family, as the type of the whole. 



Mr. Darwin, in his most interesting work upon Orchids, 

 points out that the tribe of Malaxese are distinguished 

 from Epidendreae by the absence of a caudicle to the 

 pollinia, but as some of the MalaxeaB have a minute cau- 

 dicle the division really breaks down in the most essential 

 point. 



'This is a misfortune,' he remarks h , 'which every natu- 

 ralist encounters in attempting to classify a largely de- 

 veloped or so-called natural group, in which, relatively to 

 other groups, there has been little extinction. In order 

 that the naturalist may be enabled to give precise and 

 clear definitions of his divisions, whole ranks of interme- 

 diate or gradational forms must have been utterly swept 

 away : if here and there a member of the intermediate 

 ranks has escaped annihilation, it puts an effectual bar to 

 any absolutely distinct definition/ 



In other cases a particular plant or animal may perhaps 

 have transmitted its form from generation to generation 

 almost unchanged, or, what comes to the same result, 

 those forms which diverged in character from the parent 

 stock, may have proved unsuitable to their circumstances, 

 and may have perished sooner or later. We shall then 

 find a particular form standing apart from all others, and 

 marked by various distinct characters. Occasionally we 

 h Darwin, ' Fertilization of Orchids/ p. 159. 



