354 COSMOS. 



llie combii/sd aclion of many different nilernul as well as ex- 

 ternal conditions, the nature of which can not in all cases be 

 defined, the most striking varieties being found in those fami- 

 lies which are capable of the greatest distribution over the sur- 

 face of the earth. The different races of mankind are forms 

 of one sole species, by the union of two of whose members 

 descendants are propagated. They are not different species 

 of a genus, since in that case their hybrid descendants would 

 remain unfruitful. But whether the human races have de- 

 scended from several primitive races of men, or from one alone, 

 is a question that can not be determined from experience."* 



Geographical investigations regarding the ancient scat, the 

 so-called cradle of the human race, are not devoid of a myth- 

 discussion, and north, east, and west of it, were severer during the gla 

 ciil epoch, when a great part of tlie space now occupied by the Pritish 

 isles was under watei', than they are now or were before ; but there is 

 good reason to believe that, so far from those conditions having contin- 

 ued severe, or having gradually diminished in severity southward of 

 Britain, the cold region of the glacial epoch came directly into contact 

 with a region of more southern and thermal character than that in which 

 the most southern beds of glacial drift are now to be met with. 6. This 

 state of things did not materially differ from that now existing, under 

 corresponding latitudes, in the North American, Atlantic, and Arctic 

 seas, and on their bounding shores. 7. The Alpine floras of Europe 

 and Asia, so far as they are identical with the flora of the Arctic and 

 sub- Arctic zones of the Old World, are fragments of a flora which was 

 ditfused from the north, either by means of transport not now in action 

 Du the temperate coasts of Europe, or over continuous land which no 

 »onger exists. The deep sea fauna is in like manner a fragment of the 

 general glacial fauna. 8. The floras of the islands of the Atlantic re- 

 gion, between the Gulf-weed Bank and the Old World, are fragments 

 of the great Mediterranean flora, anciently diffused over a land consti- 

 tuted out of the upheaved and never again submerged bed of the (shal- 

 low) Meiocene Sea. This great flora, in the epoch autei'ior to, and 

 probably, in part, during the glacial period, had a greater extension 

 northward than it now presents. 9. The termination of the glacial 

 epoch in Europe was marked by a recession of an Arctic fauna and flora 

 northward, and of a fauna and flora of the Mediterranean type south- 

 ward ; and in the interspace thus produced there appeared on land tha 

 Germanic fauna and flora, and in the sea that fauna termed Celtic. 

 10. The causes which thus preceded the appearance of a new assem- 

 blage of organized beings were the destruction of many species of ani- 

 mals, and probably also of plants, either forms of extremely local dis- 

 tribution, or such as were not capable of enduring many changes of con- 

 ditions — species, in short, with very limited capacity for hoi'izontal or 

 vertical diSusion. 11. All the changes before, during, and after the 

 glacial epoch appear to have been gradual, and not sudden, so that no 

 marked line of demarkation can be drawn between the creatures in- 

 habiting the same element and the same locality during two proximate 

 periods.'*] — Tr. 



* Joh. MUll(;r, PhT/siologle des Mensciien, bd. ii., s. 7G8. 



