ii6 GENERAL ORNITHOLOGY part ii 



ihe, next lesser one. Any species is teleotypic of its genus ; any genus, 

 of its family; any family, of its order; and conversely; that is to 

 say, any species represents one of the ulterior modifications of the 

 plan of its genus. The Class of Birds, for example, is one of the 

 several teleotypes of Vertebrata, i.e. of the vertebrate plan of struc- 

 ture; representing, as it does, one of several ways in which the 

 vertebrate prototype is accomplished. Conversely, the Class of 

 Birds is prototypical of its several orders, representing the plan 

 which these orders severally unfold in different ways. And so on, 

 throughout any series of animals, backward and forward in the 

 process of their evolution : any given form being teleotypic of its 

 predecessors, prototypic of its successors. All existing forms are 

 necessarily teleotypic, — only prototypic for the future. Prototype, 

 in the sense here conveyed, indicates what is often expressed by the 

 word archetype. But the latter, as I understand its use by Owen 

 and others, signifies an ideal plan never actually realised ; the 

 " archetype of the vertebrate skeleton," for example, being some- 

 thing no vertebrate ever possessed, but a theoretical model — a 

 generalisation from all known skeletons. The correspondence of my 

 use of "prototypic" with a common employment of " archetjrpic," 

 and of "teleotypic" as including both " attypic" and " etypic," is 

 noted below. 1 



The actual and visible genetic relationships of living forms being 

 practically restricted to individuals of the same species, — parents 

 and offspring specifically identical, — it would seem at first sight 

 that species must be the modified descendants of their respective 

 genera, in order to be teleotypic of any such next higher group. 

 But nothing descends from a genus, or any other group ; every- 

 thing descends from individuals ; a genus, like any other group, 

 is an abstract statement of a relation, not a begetter of anything. 

 To illustrate : the " genus Turdus " is represented, let us say, by a 

 score of species : if these species be rightly allocated in the genus, 

 they are all the modified descendants of a form which was, before 

 they severally branched off, a specific form ; and the " genus 



^ '^Archetypical characters are those which a group derives from its progenitor, 

 and with which it commences, but which in much modified descendants are lost ; 

 such, for example, is the dental formula of the Educabilia (M § PM $ C ^ 1 f x 2), 

 — a formula, as shown hy Owen, very prevalent among early members of the group, 

 but generally departed from more or less in those of the existing faunas. Attypiad 

 characters are those to the acquisition of which, as a matter of fact, we find that 

 forms, in their journey to a specialised condition, tend. . . . Mypical characters are 

 exceptional ones, and which are exhibited by an eccentric offshoot from the common 

 stock of a group " (Gill, Pr. Am. Assoc. Adv. Set, xx. 1873, p. 293). To illustrate 

 in birds : A generalised lizard-like type of sternum is archetypic of any bird's ster- 

 num. The sternum of the lizard-like animals whence birds actually descended is 

 prototypic ; the keeled sternum of a carinate bird is attypical in most birds, etypicd 

 in the peculiar state in which it is found in Stringops ; but equally teleotypic in hoth 

 instances. 



