76 GENERAL ORNITHOLOGY. 



to be teleotypic of any such next higher group. But nothiug descends from a genus, or any 

 other group ; everything descends from individuals ; a " genus," like any other group, is an ab- 

 stract statement of a relation, not a begetter of anything. To illustrate : the " genus Turdus" 

 is represented by many species : if these species be rightly allocated in the genus, they are all 

 the modified descendants of a form which vpas, before they severally branched oS', a specific 

 form; the "genus Turdus" in the abstract is simply that form; and that form is prototypic of 

 its derivatives. In the concrete, as represented by its teleotypes, the genus Turdus sums the 

 modifications which these have collectively undergone, without specifying the particular modi- 

 ficatious of any of them ; it expresses the way in which they are all like one another, and in 

 which they are all unlilce the representatives of any other genus. Thus what is above advanced 

 is seen to hold, though genera and all other groups are actual descendants of individuals 

 specifically identical. 



Generalized and Specialized Forms. — Taking any one group of animals — say the 



genus Turdus, of numerous species — and considering it apart from any other group, we per- 

 ceive that it represents a certain assemblage of characters peculiar to itself, aside from those 

 more fundamental ones it includes of its family, order, etc. Its particular characters we call 

 "generic." Among the numerous teleotypic forms it includes, there is a wide range of specific 

 variation, within the limits of generic relationship. Some of its species are modified further 

 away than some others are from the generic standard or type to which all conform more or less 

 perfectly. The former, having more peculiarities of their own, are said to be the most special- 

 ized ; the latter, having fewer peculiarities, are the least specialized. Those that are the least 

 specialized are obviously the most generalized ; and this means, that we believe them to be 

 nearest to the stock whence all have together descended with modification. The application of 

 this illustration to great groups shows us the principle upon which any form is said to be gene- 

 ralized or specialized. lehthyornis, with its fish -like vertebrse, reptile-like teeth, bird-like 

 sternum and shoulder-girdle, is a very generalized form. A Thrush is the opposite extreme of 

 a highly speciaUzed form. The two are also separated by an enormous interval of time : one 

 being very old, the other quite new ; a chronological sequence is here perceived. Since the 

 evolutionary processes concerned in the modification on the whole represent progress from sim- 

 plicity to complexity of organization, and therefore ascent in the scale of organization, a gen- 

 eralized type, an ancient type, and a simple type are on the whole synonymous, and to be 

 contrasted with specialized, recent, and complex types. They therefore respectively corre- 

 spond to 



« Low " and " High " in the Scale of Organization. — All existing birds are very 

 closely related, notwithstanding the great numerical preponderance of the class in the present 

 geological epoch. This outbreak, as it were, of birds upon the modern scene, is like the 

 nearly simultaneous bursting into bloom of a mass of flowers at the end of one branch of the 

 Sauropsidan stem. All modern birds, in fact, are strongly specialized forms, so much so that 

 it is difficult to predicate " high " or " low " within such a narrow scale. The great group 

 Passeres, for example, comprehending a majority of all known birds, is scarcely more different 

 from other birds than are the families of reptiles from each other, and among Passeres we have 

 little to go upon in deciding " high " or " low " beyond the musical ability of Oscines. It is 

 hard to see much diff"erence in actual complexity of organization between birds regarded as 

 lowest, as an Ostrich or a Penguin, and those conceded to be highest, as a Swallow or Spar- 

 row. Nevertheless, in a larger perspective, as between a fish, a reptile, and a bird, the stu- 

 dent will readily perceive the bearing of the ideas attached to the terms " low " and '' high " 

 in the scale of organization. Creatures rise in the scale by a number of correlated modifica- 

 tions and in the course of time (for it takes tim^ to evolve a class of birds from sauropsidan 



