CHAP. XIV.] CLASSIFICATION. 349 



nearly or quite lost this habit : nevertheless, without any thought 

 on the subject, these tumblers are kept in the same group, because 

 allied in blood and alike in some other respects. 



With species in a state of nature, every naturalist has in fact 

 brought descent into his classification; for he includes in his 

 lowest grade, that of species, the two sexes ; and how enormously 

 these sometimes differ in the most important charcters, is known 

 to every naturalist: scarcely a single fact can be predicated in 

 common of the adult males and hermaphrodites of certain cirri- 

 pedes, and yet no one dreams of separating them. As soon as 

 the three Orchidean forms, Monachanthus, Myanthus, and Cata- 

 setum, which had previously been ranked as three distinct genera, 

 were known to be sometimes produced on the same plant, they 

 were immediately considered as varieties ; and now I have been 

 able to show that they are the male, female, and hermaphrodite 

 forms of the same species. The naturalist includes as one species 

 the various larval stages of the same individual, however much 

 they may differ from each other and from the adult, as well as the 

 so-called alternate generations of Steenstrup, which can only in a 

 technical sense be considered as the same individual. He includes 

 monsters and varieties, not from their partial resemblance to the 

 parent-form, but because they are descended from it. 



As descent has universally been used in classing together the 

 individuals of the same species, though the males and females and 

 larvae are sometimes extremely different ; and as it has been used 

 in classing varieties which have undergone a certain, and some- 

 times a considerable amount of modification, may not this same 

 element of descent have been unconsciously used in grouping 

 species under genera, and genera under higher groups, all under 

 the so-called natural system 1 I believe it has been unconsciously 

 used ; and thus only can I understand the several rules and guides 

 which have been followed by our best systematists. As we have 

 no written pedigrees, we are forced to trace community of descent 

 by resemblances of any kind. Therefore we choose those characters 

 which are the least likely to have been modified, in relation to the 

 conditions of life to which each species has been recently exposed. 

 Rudimentary structures on this view are as good as, or even some- 

 times better than, other parts of the organisation. We care not 

 how trifling a character may be let it be the mere inflection of 

 the angle of the jaw, the manner in which an insect's wing is 

 folded, whether the skin be covered by hair or feathers if it 

 prevail throughout many and different species, especially those 

 having very different habits of life, it assumes high value ; for we 

 can account for its presence in so many forms with such different 

 habits, only by inheritance from a common parent. We may err 

 in this respect in regard to single points of structure, but when 



