xlvi PROOFS, ILLUSTRATIONS, AUTHORITIES, ETC. 



I 



the conclusions of Mr. Sedgwick, who is neither an anatomist nor a 

 naturalist, take those of the highest living authority on such sub- 

 jects, Professor Agassiz. " Nothing can be more gratifying," he 

 says, "than to trace the close agreement of the general results 

 derived from the study of the structure of animals with the results 

 derived from the investigation of their embryonic changes, or from 

 their succession in geological times. Let anatomy be the founda- 

 tion of a classification, and, in the main, the frame thus devised will 

 agree with the arrangement introduced from embryological data. 

 And again, this series will express the chief features of the order of 

 succession in which animals were gradually introduced upon our 

 globe." Lake Superior, p. 197. 



It appears, however, that some of the views which were prevalent 

 regarding embryonic changes at the time when this work first 

 appeared, are now given up, and we h'ave therefore brought forward, 

 in the present edition, an amended view of this subject: see chapter 

 entitled Hypothesis of the Development, &c. Professor Sedgwick will 

 find that the amended view only brings the phenomena of develop- 

 ment into a more perfect conformity with the history of species 

 upon the earth, and so far strengthens the general argument of the 

 present work. 



The learned Professor fills nearly a hundred pages in discoursing 

 on the geological record of life, and, while admitting " a progressive 

 development of organic structures," in a historical sense, denies that 

 " the animal remains of our successive groups of strata are presented 

 to us in such an order as to suggest a theory of natural development 

 by transmutation from one organic form to another." " Are the 

 Genera and Families of the old world," says he, " so ill-defined as to 

 pass one into another by insensible gradations ? Are the organic 

 intervals between the different orders and classes of the Animal 

 Kingdom so far interpolated by new forms of nature as to lose all 

 semblance of reality and permanence, and to show that all our syste- 

 matic lines of separation are but the artifices of immature knowledge 

 j that Order may spring from Order, and Class from Class, in the 

 way of natural generation ? Do the organic types of the old world 

 follow one another chronologically, in such a manner as to arrange 

 themselves on any conceivable organic scale, whether simple or com- 

 plicated ? To all such questions I can do no more than return a 

 most decided negative." 



The organic phenomena of geology are, by Mr. Sedgwick's own 

 admission, " widely separated, broken, and disjointed." We can 

 therefore scarcely expect to find in them the minute shades of grada- 

 tion he assumes as necessary for a theory of transmutation. The 

 theory, however, expressly leads to the expectation of considerable 

 intervals of organic character between one grade of the animal king- 

 dom and another, and it is not therefore surprising to find such 

 breaks in the palseontological record. It is nevertheless true that 

 many investigators fully equal in reputation to Professor Sedgwick, 

 or any of those whom he brings forward on his own side, do show a 



