160 ME. W. D. CBOTCU OK THE LEMMING. 



tbey did not even reach the " sunken land of Buz," to which 30° 

 W. long, and 55° 30' JN". lat. is assigned ; but it is very remark- 

 able that the average depth from Norway to Iceland does not ex- 

 ceed 250 fathoms, with the exception of a deep and narrow chan- 

 nel of 682 fathoms at 14° "W. This probably represented the old 

 gulf- stream ; and if this were so, the Lemmings did wisely to mi- 

 grate westwards in search of its genial influence. As little by 

 little the ocean encroached on the land, the same advantages 

 would remain, as in fact they do to this day. But, owing to the 

 rash confidence acquired by crossing with impunity so many lakes 

 and fjords, this singular result is arrived at, that none of the tra- 

 vellers return to teach a lesson of caution to the survivors. 



The submerged continent of Lemuria is held to explain many 

 knotty points in the distribution of animals ; and I think the ex- 

 istence of a Miocene Atlantis will be found to have a strongly 

 elucidative bearing on subjects of even more interest than the mi- 

 gration of the Lemming. It is difficult to ascertain with any cer- 

 tainty the duration of life in these animals, since very few meet 

 with a natural death. It is, however, clear that they survive the 

 winter ; and one which I have in captivity, as well as those now in 

 the Zoological Grardens, are at least three months old. But the fact 

 that the young soon leave their common nest and join the general 

 band of migrants shows, I think, that they are actuated by a com- 

 mon impulse which is neither deficiency of food nor a mere gra- 

 vitating tendency to roll down hill. It is true that many other 

 animals share this tendency to westward migration ; but that fact 

 only intensifies the need of a satisfactory explanation, for which, 

 until a better is found, I am constrained to propose the Miocene 

 Atlantis*. 



DESCRIPTION OF PLATE XIII. 

 Fig. 1. Chart of Scandinavia. The two main valleys, Gudbrandsdalen and 



the valley of the Glommen, run nearly north and south. The course 



of the Lemmings crosses these at right angles. 

 Fig. 2. In this plan of Heimdalen, drawn to scale, the course of the Lemmings 



will be seen to cross the Lake Heimdalsvand and the swift river 



Leirungen, both of which might be avoided by a slight detour. 

 Fig. 3. A section of the same, showing the Lemmings' track, which does not 



follow the watershed. 

 The rivsr Leirungen is of glacier origin, very cold and very rapid. Dogs do 

 not like to face it ; and yet the Lemmings cross it in thousands. 



* [ Vide Note " On the occurrence of the Lemming in Newfoundland," Zoo- 

 logist, Feb. 1877, p. 47.— Ed.] 



