Professor Duns on the Migration of Mammals. 199 



example, by the fact of the presence of one of the Hystricidce 

 outside of the sub-regions to which this family has been 

 relegated. The term migration was used as inclusive, both 

 of seasonal changes and of those which occur at irregular in- 

 tervals. Schinz, of Zurich, had held that in the case of 

 birds their breeding place should be regarded as their home. 

 This is truer of mammals. In many instances birds occa- 

 sionally nest far from the area of chief distribution, as in 

 Scotland, the red backed shrike (Lanius collurio), the wood- 

 cock {Scoloimx rusticola), the stockdove {Golmiiba cenas), etc. 

 The occurrence of the remains of the great extinct mammals 

 in British deposits does not determine the question of climate, 

 it only asks, is there anything in the migration of recent 

 forms to shed light on this ? It was pointed out how much 

 light might be shed on some of those topics by a thoughtful 

 estimate of man's migrations, looked at in the light of his 

 relations to the fauna with which he comes in contact. 

 " Avoiding ' stock' illustrations," he said, " the subject falls to 

 be considered under three heads — 1. Periodic Migrations ; 

 2. Seasonal Migrations ; and 3. Partial Migrations, Seasonal 

 and Periodic." The first was fully illustrated by reference to 

 the wanderings of the northern grey squirrel {Sciurus migra- 

 torius) and the Lemming {Myoclus lemmus). Olaus Wormius, 

 Pontippidan, Linnseus, Cuvier, Audubon, and Bachman, etc., 

 w^ere cited as authorities. It was shown that neither the 

 theory of temperature, nor of breeding, nor of food, sheds any 

 light on these movements, because ten, thirteen, eighteen, or 

 over twenty years are known to have intervened between 

 one great migration and another. It was asked, " Is this the 

 action of a check on over-productiveness — a provision for 

 maintaining the balance among living forms ? Have we 

 analogous instances in recent years in the plagues of a related 

 form (Arvicola agrestis) in France, Belgium, England, and 

 Scotland ? And are they drawn away from localities in 

 which they have become too numerous, by an inherited im- 

 pulse towards their ancestral homes ?" 



The reindeer (Cervus tarandus) was referred to in illustration 

 of Seasonal Migrations. Von Wrangel, Piichardson, and Nor- 

 denskjold were quoted. Having noticed the explanation of 



