216 CLASSIFICATION. [Chap. XIV. 



important character of the length of the beak, yet all 

 are kept together from havmg the common habit of 

 tumbling ; but the short-faced breed has 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 characters, is known to every 

 naturalist : scarcely a single fact can be predicated in 

 common of the adult males and hermaphrodites of 

 certain cirripedes, and yet no one dreams of separating 

 them. As soon as the three Orchidean forms, Mo- 

 nachanthus, 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 tliey are descended from it. 



As descent has universally been used in classing 

 together the individuals of the same species, thougli the 

 males and females and larvae are sometimes extremely 

 different ; and as it has been used in classiucr varieties 



