66 Darwin, and after Darwin. 
Now, rudimentary organs of this kind are of such 
frequent occurrence, that almost every species presents 
one or more of them—usually, indeed, a considerable 
number. How, then, are they to be accounted for? 
Of course the theory of descent with adaptive modifi- 
cation has a simple answer to supply—namely, that 
when, from changed conditions of life, an organ which 
was previously useful becomes useless, it will be suf- 
fered to dwindle away in successive generations, under 
the influence of certain natural causes which we shall 
have to consider in future chapters. On the other 
hand, the theory of special creation can only maintain 
that these rudiments are formed for the sake of ad- 
hering to an ideal type. Now, here again the former 
theory appears to be triumphant over the latter ; for, 
without waiting to dispute the wisdom of making 
dwarfed and useless structures merely for the whim- 
sical motive assigned, surely if such a method were 
adopted in so many cases, we should expect that in 
consistency it would be adopted in all cases. This 
reasonable expectation, howevcr, is far from being 
realized. We have already seen that in numberless 
cases, such as that of the fore-limbs of serpents, no 
vestige of a rudiment is present. But the vacillating 
policy in the matter of rudiments does not end here; 
for it is shown in a still more aggravated form where 
within the limits of the same natural group of or- 
ganisms a rudiment is sometimes present and some- 
times absent. For instance, although in nearly all the 
numerous species of snakes there are no vestiges of 
limbs, in the Python we find very tiny rudiments of the 
hind-limbs. (Fig. 8.) Now, is ita worthy conception of 
Deity that, while neglecting to maintain his unity of 
