IT 2 Eepoet of the State Geologist. 



idea of natural classification we must no longer allow ourselves 

 to appeal to any single characteristic no matter how convenient 

 or easy of observation it may be ; we must take into account as 

 far as possible the entirety of the organism. Classifications 

 where the divisions are founded each on a single character may 

 afford a certain means for facility in quick determinations ; these 

 are systetns. The word method should be reserved for the 

 natural classification. This could only be finally established if 

 all organisms, both living and fossil, were completely known, but 

 we can strive toward its attainment by successive approximations. 



The transformist doctrine has suddenly thrown much light on 

 the problem of classification ; it has freed the idea of natural 

 classification from whatever was obscure and metaphysical. 

 The principle of descent once established, aflinities explain them- 

 selves by the relations of parentage, and natural classification is 

 nothing else than Phylogeny. 



It is easy to understand the interest which attaches to the dis- 

 covery of the genealogic tree of organisms which exist or have 

 existed in remote epochs. One of the most illustrious teachers 

 of the transformist school, Haeckel, has won great distinction by 

 his essays in this direction, and his principal works, " Anthrojpch 

 geny^^ and '^ Natural Creation^'* raised polemic discussions, the 

 echoes of which have not yet ceased. 



Palaeontology stands in the first rank among the natural 

 sciences which have advanced our knowledge of Phylogeny. 

 At every page we shall have occasion to indicate to what point 

 we have actually attained in the connection of extinct forms either 

 with each other or with forms now living. We must, therefore, 

 bestow some attention on the processes whereby the relations of 

 parentage among organisms are determined. These processes 

 may be referred to three general methods, two of which apply 

 equally to living or extinct types, while the third, founded solely 

 on the relations of Palaeontology and Stratigraphy, is conse- 

 quently applicable only to fossil forms. 



§ 2. Method of Comparative Anatomy. 



Evolution of organs. — If there really exists a filiation between 

 the creatures of the present day and those of former times; if, 



