38 Evolution and Adaptation 



arrange these organs in definite series passing from the 

 simple to the complex, or, in case of degeneration, in the 

 reverse order. However convenient it may be to study 

 the structure of organisms from this point of view, the arti- 

 ficiality of the procedure will be obvious, since here also the 

 organs of any two species do not differ from each other in 

 only one point, but in many, perhaps in all. Therefore to 

 arrange or to compare them according to any one scheme 

 gives only an incomplete idea of their structure. We should 

 apply here the same point of view that we used above in 

 forming a conception of the meaning of the zoological and 

 botanical systems. We must admit that our scheme is only 

 an ideal, which corresponds to nothing real in nature, but 

 is an abstraction based on the results of our experience. 

 It might be a pleasing fancy to imagine that this ideal 

 scheme corresponds to the plan of structure or of organiza- 

 tion that is in every egg, and furnishes the basis for all the 

 variations that have come or may come into existence ; but 

 we should find no justification whatsoever for believing that 

 our fiction corresponds to any such real thing. 



To sum up the discussion : we find that the resemblances 

 of animals and plants can be accounted for on the transmu- 

 tation theory, not in the way commonly implied, but in a some- 

 what different sense. We have found that the resemblances 

 between the different members of a group are only of a 

 very general sort, and the structures are not identically the 

 same in any two species — in fact, perhaps in no two indi- 

 viduals. This conclusion, however, does not stand in con- 

 tradiction to the transmutation hypothesis, because, since 

 each individual begins as an egg which is not a replica of 

 the original adult from which it is derived, there can be no 

 identity, but at most a very close similarity. Admitting, then, 

 that our scheme is an ideal one, we can claim, nevertheless, 

 that on this basis the facts of classification find a legitimate 

 explanation in the transmutation theory. 



