380 THE ORIGIN OF SPECIES 



purpose with cattle, because they are less variable than the shape 

 or color of the body, etc.; whereas with sheep the horns are much 

 less serviceable, because less constant. In classing varieties, I ap- 

 prehend that if we had a real pedigree, a genealogical classification 

 would be universally preferred; and it has been attempted in 

 some cases. For we might feel sure, whether there had been more 

 or less modification, that the principle of inheritance would keep 

 the forms together which were allied in the greatest number of 

 points. In tumbler pigeons, though some of the sub-varieties differ 

 in the important character of the length of the beak, yet all are 

 kept together from having the common habit of tumbling; but 

 the short-faced breed has nearly or quite lost this habit ; neverthe- 

 less, 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 low- 

 est 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 Com- 

 mon of the adult males and hermaphrodites of certain cirripedes, 

 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 

 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? I believe it has been unconsciously 

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



