THE ORIGIN OF SPECIES. 19 



and overtop on all sides many a feebler branch, so by genera- 

 tion I believe it has been with the great Tree of Life, which fills 

 with its dead and broken branches the crust of the earth, and 

 covers the surface with its ever-branching and beautiful ramifi- 

 cations." 



It may also be noted that there is a significant cor- 

 respondence between the rival theories as to the main 

 facts employed. Apparently every capital fact in the 

 one view is a capital fact in the other. The difference 

 is in the interpretation. To run the parallel ready 

 made to our hands : l 



"The simultaneous existence of the most diversified types 

 under identical circumstances, .... the repetition of similar 

 types under the most diversified circumstances, .... the unity 

 of plan in otherwise highly-diversified types of animals, .... 

 the correspondence, now generally known as special homologies, 

 in the details of structure otherwise entirely disconnected, down 

 to the most minute peculiarities, .... the various degrees and 

 different kinds of relationship among animals which (apparently) 

 can have no genealogical connection, .... the simultaneous 

 existence in the earliest geological periods, . . . . of representa- 

 tives of all the great types of the animal kingdom, .... the 

 gradation based upon complications of structure which may be 

 traced among animals built upon the same plan ; the distribu- 

 tion of some types over the most extensive range of surface of 

 the globe, while others are limited to particular geographical 

 areas, .... the identity of structures of these types, notwith- 

 standing their wide geographical distribution, .... the com- 

 munity of structure in certain respects of animals otherwise en- 

 tirely different, but living within the same geographical area, 

 .... the connection by series of special structures observed 

 in animals widely scattered over the surface of the globe, .... 

 the definite relations in which animals stand to the surrounding 

 world, .... the relations in which individuals of the same 



1 Agassiz, " Essay on Classification ; Contributions to Natural His- 

 tory," p. 132, et seq. 



