071 the Origin of SjJecies, 117 



sands of Canada. These belong to a period of elevation proceed- 

 ing gradually from tlie time of the boulder formation up to the 

 modern era. In these deposits we have more than stxty species of 

 invertebrate animals, all except one or two known to be now living 

 in the Gulf of St. Lawrence. Yet in all thia lapse of time not one 

 of the species has, by natural selection or any other cause, varied 

 more than its living relatives now do. Still further, one or two 

 species, as the Leda truncata and Triclwtropis arctlca, now found 

 only in the Arctic seas, are quite like their modern representatives 

 in those distant waters. They had plenty of time to vary, in 

 order to suit the new circumstances, but they could not. Further, 

 at the same time when these shells lived in the plains of Canada, 

 Arctic plants, conveyed probably by ice, became settled on the 

 White Mountains, the descendants of which still remain isolated 

 but unchanged. Such facts as these are conclusive, notwithstand- 

 ing the imperfection of the geological record on other points. 



In one point our author endeavors to find support to his 

 views from geological evidence, in the resemblance of successive 

 faunas of the same locality to each other. The extinct ter- 

 tiary animals of South America, New Zealand and Australia, 

 for example, are like in type to those now inhabiting the same 

 regions. But then we have no connecting links, and hence it seems 

 more probable that successive creations were conformed to the 

 same generic types, because the physical conditions remained 

 unchanged, than that the modern sloths, for example, are degene- 

 rate descendants of the Megatheria. Farther, it does not seem 

 to have occurred to Mr. Darwin that these resemblances are 

 confined to the southern hemisphere. They do not obtain at all 

 in North America, in Northern Asia, in Europe. In these coun- 

 tries new types have replaced the old, and certain old species, 

 like the musk ox, the megaceros, the beaver, the aurochs, 

 have become locally or wholly extinct, instead of undergoing 

 change. All this has happened no doubt because the modern 

 conditions are too dissimilar from the ancient to permit the con- 

 tinuance of old forms under any variety of them, and thus new 

 forms have been introduced. 



In his closing chapters the author endeavours to shew that his 

 theory accounts in a satisfactory manner for the typical likeness 

 of species to each other, for the curious embryological relations 

 of animals, and for the existence of rudimentary organs ; but all 

 these things are equally intelligible on the opposite view. If spe- 



