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THE AMERICAN NATURALIST [Vol. L 



Adams 3 did good service iti bringing together a number of sug- 

 gested "criteria for the determination of centers of dispersal.'' 

 It was not to be expected, and doubtless Adams did not expect, 

 that all of them would stand up under a test. Without attempt- 

 ing to exhaust the subject, present anything new or review all 

 that has been said about them, certain notes may be made in 

 connection with this discussion, taking up the criteria seriatim. 



1. Location of the Greatest Differentiation of the Type.— I be- 

 lieve it is more than a mere question of definition to say that the 

 offering of this criterion is an instance of the confusion of ' ' cen- 

 ter of dispersal" with "center of greatest development." Two of 

 the stock illustrations of great differentiation are those of mar- 

 supials in Australia and lemurs in Madagascar. Since these 

 groups are so greatly developed on the respective islands they 

 should, according to this criterion, have spread out from these 

 islands to the rest of the world. Unless the paleontological evi- 

 dence, as brought together and interpreted by Matthew, is false, 

 that was not the history of these cases. On the other hand, wher- 

 ever their points of origin were, their ancestors got into the 

 Holarctic region and then spread in various directions. Xow, if 

 this be true, their center of dispersal would be Holarctica, al- 

 though their greatest differentiation at flu p>rs< at tune is toward 

 the other end of the world. Lest the quibble should be raised by 

 others, it should be stated that the real fundamental center of 

 dispersal of a group is its center of origin and that there are 

 3C. C. Adams, 1902, "Southeastern United States as a Center of Dis- 

 tribution of Flora and Fauna," Biol. Bull., VII, p. 122. After the pres- 

 ent paper had gone to the press I obtained through the kindness of Pro- 

 fessor Adams, a portion of "An Ecological Survey of Isle Royale, Lake 

 Superior" prepared under his direction and published (1909) as a part 

 of the Report of [Michigan] Board of the Geological Survey for 1908. In 

 this he takes up, again, these criteria. He says "It should be clearly em- 

 phasized that it is the convergence of evidence from many criteria which 

 must be the final test in the determination of origins rather than the de- 

 pendence upon any supposedly absolute criterion. ' ' He discusses the vari- 

 ous criteria in greater detail than was done in his 1902 paper and adds, as 

 another criterion, "Direction indicated by seasonal appearance; vernal 

 suggesting boreal or montane origin and aestival as austral or lowland 

 derivation." I regret that I did not have earlier access to this paper but 

 as I did not base my present remarks on his 1902 contribution with the 

 idea of criticizing it in particular but for the purpose of pointing out the 

 danger of relying too confidently on such evidence, it is probably unneces- 

 sary to change the text of this article in order to meet the expanded dis- 

 cussion in the 191.9 paper by Adams. This is especially true since I in- 

 such as the one by Tower (1906), which bear 'on theTa^Lbiect" 1 ^ 



