25X) FROM NORTH POLE TO EQUATOR. 



for the migrating whales to keep neither to time nor to route; in 

 general, their journeys are as regular as if they were arranged 

 according to the position of the stars, and as if they took place 

 along laid-out paths bounded on both sides. No other mammal 

 migrates more regularly; indeed, their wanderings may be compared 

 with the migrations of birds. 



The seals, like the whales, migrate every year, on the whole with 

 great regularity, though not to such a distance. Those species which 

 inhabit inland seas cannot, of course, leave these, but they traverse 

 them every year in regular order, or at certain times ascend the 

 rivers flowing into them; all the ocean species, on the other hand, 

 set out every autumn and spring, by definite routes, to certain 

 regions or localities. All the seals in the far north, as well as those 

 in the seas about the South Pole, are forced to migrate by the exten- 

 sion of the ice in winter, and may travel with it towards temperate 

 zones, returning towards the poles again as the ice melts. But they, 

 like all other members of their order, are impelled to travel for an- 

 other not less weighty reason ; they require the mainland, or at least 

 large, spreading, fixed masses of ice, on which to bring forth and 

 nurture their young, until these are able to follow them into the 

 water, there to shift for themselves. Thus every year thousands 

 and hundreds of thousands of seals appear on certain islands and 

 ice-banks, covering some of these birth-places of their race in such 

 crowds that every available spot must be utilized in order to secure 

 space for all to bring forth their young. They pass weeks, even 

 months, on land or on the ice without hunting, descending into the 

 sea, or taking food; they suckle their young, then mate, and by 

 degrees break up their great assemblage, distributing themselves 

 over the wide ocean to resume their former manner of life, or setting 

 out with their young, who still require training, on more or less 

 extensive foraging expeditions. 59 



As is well known, there are many mammals which have the habit 

 of hibernating, which pass the severe part of the year well protected 

 in deep and carefully closed burrows, and are thus spared the neces- 

 sity of leaving their haunts. Even among these, however, at least 

 among those living in the temperate zones, there are some which 



