8 Berry — Present Tendencies in Paleontology. 



cially true of the work of Ettingshausen, Geinitz, 

 Lesquereux, and their contemporaries in Carboniferous 

 paleobotany. Even where identity seems assured as in 

 dealing with cortical remains of forms like Sigillaria and 

 Lepidodendron, assumed cosmopolitanism is vitiated by 

 the discovery that identical surface form between speci- 

 mens from Europe and America was accompanied by 

 slight differences in anatomy or specific differences in 

 cone structure. 



From Moses' account of the spread of the passengers 

 of Noah's ark to Matthew's recently published Climate 

 and Evolution, many attempts have been made to explain 

 the origin and migration of organisms. It has taken a 

 long time for naturalists to realize that modern distri- 

 bution has its key in ancestral distribution, or to dis- 

 criminate the fluctuation of life zones from such very 

 different seasonal phenomena as are displayed by the 

 migratory birds. It would perhaps be better to elimi- 

 nate the word migration altogether and use the term dis- 

 persal, since the criteria of voluntary and involuntary 

 action are of extremely doubtful validity. 



The time of origin of an organic type or assemblage, 

 the place of origin, the area once occupied and the time 

 of extinction or the area now occupied, are among the 

 most important questions with which we have to deal. 

 Obviously without the correct chronology such questions 

 are insoluble, hence the importance of far flung correla- 

 tions and the need for the most critical criteria for 

 correlation. 



Similar successions of fossil-bearing sediments in dif- 

 ferent areas naturally resulted in this correspondence 

 being considered indicative of synchroneity. Huxley in 

 his anniversary address to the Geological Society of 

 London in 1862 was the first serious critic of this concep- 

 tion. He, as you know, proposed the term homotaxis for 

 the alternative idea due to the necessity of taking into 

 account the time consumed in the dispersal of organisms. 

 Those who adopt the latter and apparently reasonable 

 assumption sometimes take the position (E. Forbes, N. S. 

 Shaler) that similarity of organic content, instead of 

 being indicative of chronologic synchroneity, proves that 

 the compared deposits could not have been contempora- 

 neous. Conceding that this view grossly exaggerates the 

 importance of the time element, it is to be noted that of 



