RUDIMENTARY ORGANS 269 



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 afterward wholly 

 disappear. It is also, I believe, a universal rule, that a 

 rudimentary part is of greater size in the embryo rela- 

 tively to the adjoining parts 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 

 ru.dimentary 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 reason- 

 ing power which 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," or in order "to 

 complete the scheme of nature." But this is not an ex- 

 planation, merely a restatement of the fact. Nor is it con- 

 sistent with itself: thus the boa-constrictor has rudiments 

 of hind-limbs and of a pelvis, and if it be said that these 

 bones have been retained "to complete the scheme of 

 nature," why, as Professor Weismann asks, have they 

 not been retained by other snakes, which do not possess 

 even a vestige of these same bones? What would be 

 thought of an astronomer who maintained that the satel- 

 lites revolve in elliptic courses round their planets "for 

 the sake of symmetry," because the planets thus revolve 

 round the sun? An eminent physiologist accounts for 

 the presence of rudimentary organs by supposing tliat 



