372 CLASSIFICATION. [Chap. XIV. 



■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 ; lor he includes in his 

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

 these sometimes differ in the most important characters, 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 Catasetum, 

 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 larva? are sometimes extremely different ; and as it has been 

 used in classing varieties which have undergone a certain, and 

 sometimes 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 ? 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 



