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. 
