16 GENERAL EVOLUTION". 



Plainly enough, tlien, nothing ever originated by natural se- 

 lection, and as the present essay relates to the origin of types, lit- 

 tle space can be given to its discussion ; for natural selection, 

 important though it be, is but half the question, and indeed the 

 lesser half. It is to the great causa,tive forces as are the gutters 

 and channels which conduct the water in comi^arison with the 

 pump and the man who pumps it. 



3. On Teleology. 



Two classes of structures have been alluded to : those which 

 are useful to an animal, and those which are not useful ; or the 

 adaptive and non-adaptive. Nothing is better known than that 

 animals are well adapted to their situations in the w^orld, and for 

 their needs as to sujDplying themselves with food, etc. Some part 

 of every species is so constructed as to enable it to live under con- 

 ditions where most other kinds of animals would perish. Thus 

 the sea-rangers, among birds, as the great albatross, etc., possess 

 long and pointed wings ; while those that live in thickets or 

 under cover have short, round ones, as grouse, woodcock, etc. 

 Even our sparrows — those that love the bushes and swamps, as 

 the song-sparrow {Melosjnza melodia) — have short, rounded wings, 

 while those that haunt trees have them sharper and pointed, as 

 the chipping and tree sparrow {Spizella socialis, pusilla, etc.). 

 Water-frogs have their feet webbed ; land-frogs have small or no 

 webs ; while tree-toads possess sucker-like expansions of the ends 

 of the toes, which secrete a glutinous fluid, by which they adhere 

 to the trunks and leaves of trees. Finally, frogs that burrow have 

 one or more of the bones of the base of the hind foot {tarsus) 

 modified into a projecting blade, like that of a shovel ; and, as they 

 squat down, they literally sit into the ground, and are soon out 

 of sight in the hole which they dig with these busy trowels. 



Cave insects have long and delicate antennae and limbs, ex- 

 ceeding those of their out-door relations by much. Moreover, 

 their usual lack of eyes is a clear case of the reverse of adaptation, 

 i. e., the absence of an organ where not needed. 



Less attention has been directed to the non-adaptive charac- 

 ters, yet they are as numerous as the adaptive. I do not include 

 under this head useless organs or parts only, but also those which 

 are useful, but whose peculiarities do not relate to that use as 

 advantageous to it. 



Notable examples of this kind are to be found in the characters 



