THE ARGUMENTS FROM MORPHOLOGY. 475 



tion but which, by detaining small foreign bodies, often causes 

 severe inflammation and death. The doctrine of typical plans 

 is equally out of court; for while, in some members of a 

 group, rudimentary organs completing the general type are 

 traceable, in other members of the same group such organs 

 are unrepresented. There remains only the doctrine of evolu- 

 tion; and to this, these rudimentary organs offer no diffi- 

 culties. On the contrary, they are among its most striking 

 evidences. 



§ 136. The general truths of morphology thus coincide in 

 their implications. Unity of type, maintained under extreme 

 dissimilarities of form and mode of life, is explicable as re- 

 sulting from descent with modification; but is otherwise in- 

 explicable. The likenesses disguised by unlikenesses, which 

 the comparative anatomist discovers between various organs 

 in the same organism, are worse than meaningless if it be 

 supposed that organisms were severally framed as we now 

 see them; but they fit in quite harmoniously with the belief 

 that each kind of organism is a product of accumulated modi- 

 fications upon modifications. And the presence, in all kinds 

 of animals and plants, of functionally-useless parts corre- 

 sponding to parts that are functionally-useful in allied ani- 

 mals and plants, while it is totally incongruous with the belief 

 in a construction of each organism by miraculous interposi- 

 tion, is just what we are led to expect by the belief that organ- 

 isms have arisen by progression. 



