DESCENT OF MAN FROM SOME LOWER F0B3I. 137 



surrounding conditions, have been suddenly produced; 

 and of such complex and wonderful coadaptations he 

 will not be able to assign a shadow of an explanation. 

 He will be forced to admit that these great and sudden 

 transformations hare left no trace of their action on the 

 embryo. To admit all this is, as it seems to me, to enter 

 into the realms of miracle, and to leave those of science. 



KUDIMENTAET OEGANS ONLY TO BE EXPLAINED ON THE 

 THEOET OF DEVELOPMENT. 



Descent of ^^t one of the higher animals can be 



Man, page named which does not bear some part in a 

 _J_^ rudimentary condition ; and man forms no ex- 

 ception to the rule. Budimentary organ s must be dis- 

 tinguished from those that are nascent, though in some 

 cases the distinction is not easy. The former are either 

 absolutely useless, such as the mammae of male quadru- 

 peds, or the incisor teeth of ruminants which never cut 

 through the gums ; or they are of such slight service to 

 their present possessors that we can hardly suppose that 

 they were developed under the conditions which now ex- 

 ist. Organs in this latter state are not strictly rudiment- 

 ary, but they are tending in this direction. N^ascent 

 organs, on the other hand, though not fully developed, 

 are of high service to their possessors, and are capable of 

 further development. Rudimentary organs are eminently 

 variable ; and this is partly intelligible, as they are use- 

 less, or nearly useless, and consequently are no longer 

 subjected to natural selection. They often become wholly 

 isnppressed. When this occurs, they are neyertheless 

 liable to occasional reappearance through reversion — a 

 circumstance well worthy of attention. 



