334 EVOLUTION OF TO-DAY. 



planation partly satisfactory has been offered. The 

 classification of animals and the relation of species 

 to each other have revealed a bond uniting the 

 organic world into a unit. They have proved that 

 there has been some connection between all organ- 

 isms, and the assumption that this bond of connec- 

 tion is heredity has been found to meet the require- 

 ments of the case. The order of appearance of 

 animals in the past has further testified to this as- 

 sumption, since they have been found to appear in 

 the order which the theory would expect. Although 

 the sudden appearance of a highly diversified fauna 

 in the earliest rocks which give us any record is 

 somewhat of a surprise, yet the evidence elsewhere 

 has been conclusive. Still more forcibly has this 

 same uniting bond been proved by embryology. 

 Here, too, in a marvellous manner has the evidence 

 pointed to heredity as this bond. Until to-day the 

 subject of classification, paleontology, embryology, 

 and genetic descent are so intimately combined that 

 it is no longer possible to separate them. Finally, 

 the geographical distribution of animals has offered 

 its evidence, and in some cases, /. e., oceanic 

 islands, has presented a practical demonstration 

 that new species can arise from old ones. 



All of this evidence together forms an argument 

 that no one who has carefully studied the matter 

 has been inclined to deny. It is true that all of the 

 difficulties have not yet been cleared away, and that 

 some of them seem to indicate that there are other 

 laws of life not comprised in the theory of evolu- 

 tion. Beyond difficulties of detail, which of course 



