472 C. L. HUBBS 



raphers not long ago threw around with abandon. King (1) assures 

 us that geologists hold to the theory of the essential permanence of 

 the ocean basins, and the biologists seem to have proceeded on this 

 assumption. The verified intercontinental connections across the 

 Isthmus of Panama and especially across the Bering Strait region 

 are duly treated. The intimate relationships between the Palearctic 

 and Nearctic faunas are pointed out by Parkes (16) and other 

 authors, and are rightly assumed to indicate a past continuity, but, 

 as Burt (5), Rehn (12), and Hovanitz (14) point out with admirable 

 reserve, there is, as yet, usually little basis for postulating the region 

 of origin and the direction of dispersal. In some groups there may 

 have been a complex interchange. 



In general, it is admitted, or apparently assumed, that the recon- 

 struction of the past history of a group, whether of origin or dis- 

 persal, cannot ordinarily be postulated with assurance on the sole 

 basis of the present distributional pattern. Considerable variance in 

 reserve or reliance, however, is displayed in such reconstructions. 

 Bartholomew (3) and Burt (5) go so far as to say there are no 

 separate "origins," because there has been a continuum of life, but 

 are they not playing with semantics? In terms of given natural 

 groups or stages of evolution there is an origin, in both time and 

 space. 



The criteria of center of origin, or of differentiation, as some would 

 prefer to say, are definitely discussed by only two of the authors, 

 D. E. Savage (4) and Burt (5). Savage's criteria are the more impres- 

 sive because they emphasize the fossil record. His first criterion of 

 area of origin is the region from which the oldest fossil is known. 

 This is fine for groups with a well-known fossil record, but for groups 

 with few known fossils may, as Parkes (16) notes, be even more 

 treacherous than criteria based on present distributions. Savage's 

 second criterion is an earlier record of progenitors (the sort of 

 evidence that puts man's origin securely in the Old World) — again 

 good, if the data are adequate. His third criterion is the area of 

 greatest taxonomic diversity. This criterion may usually hold, but 

 certainly not always. It seems not to apply, for example, to the 

 origin of the catostomid fishes, which are almost restricted to North 

 America, but which R. R. Miller (9) and I believe, on scanty but 

 pertinent distributional and fossil evidence, to have originated in 

 Asia, though they seem to have undergone most of their difi^erentia- 



