Chap. XIV.] AND ABORTED ORGANS. 259 



which analogy would lead us to expect to find in them, 

 and which are occasionally found in monstrous indivi- 

 duals. Thus in most of the Scrophulariacese the fifth 

 stamen is utterly aborted ; yet we may conclude that a 

 fifth stamen once existed, for a rudiment of it is found 

 in many species of the family, and this rudiment 

 occasionally becomes perfectly developed, as may some- 

 times be seen in the common snap-dragon. In tracing 

 the homologies of any part in different members of the 

 same class, nothing is more common, or, in order fully 

 to understand the relations of the parts, more useful 

 than the discovery of rudiments. This is well shown 

 in the drawings given by Owen of the leg-bones 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 is of greater size in the embryo 

 relatively to the adjoining parts, than in the adult ; so 

 that the organ at tliis early age is less rudimentary, or 

 even cannot be said to be in any degree rudimentary. 

 Hence rudimentary organs in the adult are often said 

 to have retained their 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 

 reasoning power wliich tells us 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 

 on natural history, rudimentary organs are generally 

 said to have been created " for the sake of symmetry," 

 40 



