68 Darwin, and after Darwin. 
dwindling due to inutility. Thus, for example, to 
return to the case of wings, we have already seen 
that in an extinct genus of bird, Dinornis, these 
organs were reduced to such an extent as to leave 
it still doubtful whether so much as the tiny rudiment 
hypothetically supplied to Fig. 6 (p. 61) was present 
in all the species. And here is another well-known 
case of another genus of still existing bird, which, as 
was the case with Dixornis, occurs only in New 
Zealand. (Fig. 9.) Upon this island there are no four- 
footed enemies—either existing or extinct—to escape 
from which the wings of birds would be of any service. 
Consequently we can understand why on this island 
we should meet with such a remarkable dwindling 
away of wings. 
Similarly, the logger-headed duck of South America 
_can only flap along the surface of the water, having 
_its wings considerably reduced though less so than 
\the Apteryx of New Zealand. But here the interesting 
\fact is that the young birds are able to fly perfectly 
‘well. Now, in accordance with a general law to be 
.considered in a future chapter, the life-history of an 
individual organism is a kind of condensed recapitu- 
lation of the life-history of its species. Consequently, 
we can understand why the little chickens of the 
logger-headed duck are able to fly like all other ducks, 
while their parents are only able to flap along the 
surface of the water. 
Facts analogous to this reduction of wings in birds 
which have no further use for them, are to be met 
with also in insects under similar circumstances. 
Thus, there are on the island of Madeira somewhere 
between 500 and 600 species of beetles, which are in 
