'Chap. XIII. 
EUDIMENTAEY OEGANS. 
453 
and in other respects. Moreover, in closely allied 
species, the degree to which the same organ has been 
rendered rudimentary occasionally differs much. This 
latter fact is well exemplified in the state of the wings 
of the female moths in certain groups. Rudimentary 
organs may be utterly aborted; and this implies, that 
we find in an animal or plant no trace of an organ, 
which analogy would lead us to expect to find, and 
which is occasionally found in monstrous individuals 
of the species. Thus in the snapdragon (antirrhinum) 
we generally do not find a rudiment of a fifth stamen; 
but this may sometimes be seen. In tracing the homo¬ 
logies of the same part in different members of a class, 
nothing is more common, or more necessary, than the 
use and discovery of rudiments. This is well shown in 
the drawings given by Owen of the bones of the leg of 
the horse, ox, and rhinoceros. 
It is an important fact that rudimentary organs, such 
as teeth in the upper jaws of whales and ruminants, 
can often be detected in the embryo, but afterwards 
wholly disappear. It is also, I believe, a universal 
rule, that a rudimentary part or organ is of greater 
size relatively to the adjoining parts in the embryo, 
than in the adult; so that the organ at this early age 
is less rudimentary, or even cannot be said to be in any 
degree rudimentary. Hence, also, a rudimentary organ 
in the adult is often said to have retained its embryonic 
condition. 
I have now given the leading facts with respect to 
rudimentary organs. In reflecting on them, every one 
must be struck with astonishment: for the same reason¬ 
ing power which tells us plainly that most parts and 
organs are exquisitely adapted for certain purposes, 
tells us with equal plainness that these rudimentary or 
atrophied organs, are imperfect and useless. In works 
