20 G THE CRUISE OF THE BETSEY j OB, 



the bricks are always the same. It is not so in nature. The 

 bricks are as dissimilar as the houses. We find, for instance, 

 those differences, specific and generic, that obtain among fishes, 

 both recent and extinct, descending to even the microscopic 

 structure of their teeth. There is more variety of pattern, 

 in most cases of very elegant pattern, in the sliced frag- 

 ments of the teeth of the ichthyolites of a single formation, 

 than in the carved blocks of an extensive calico-print yard. 

 Each species has its own distinct pattern, as if in all the in- 

 dividuals of which it consisted the same block had been em- 

 ployed to stamp it ; each genus has its own general type of 

 pattern, as if the same inventive idea, variously altered and 

 modified, had been wrought upon in all. In the genus Den- 

 drodus, for instance, it is the generic type, that from a cen- 

 tral nave there should radiate, spoke-like, a number of leafy 

 branches ; but in the several species, the branches, if I may 

 so express myself, belong to different shrubs, and present dis- 

 similar outlines. There are no repetitions of earlier patterns 

 to be found among the generically different ichthyolites of other 

 formations. We see in the world of fashion old modes of 

 ornament continually reviving : the range of invention seems 

 limited ; and we find it revolving, in consequence, in an ir- 

 regular, ever-returning cycle. But Infinite resource did not 

 need to travel in a circle, and so we find no return or doub- 

 lings in its course. It has appeared to me, that an argument 

 against the transmutation of species, were any such needed, 

 might be founded on those inherent peculiarities of structure 

 that are ascertained thus to pervade the entire texture of the 

 framework of animals. If we find one building differing 

 from another merely in external form, we have no difficulty 

 in conceiving how, by additions and alterations, they might 

 be made to present a uniform appearance : transmutation, 

 development, progression, if one may use such terms, 

 possible in such circumstances. But if the buildings 



