32 



ARCTIC PROVINCE. 



the most unprolific, and we have to descend into 

 the depths to find an abundance of ground-living 

 creatures, which moreover appear to range much 

 deeper in high latitudes than they do in more 

 favourable climes. Their bathymetrical range will, 

 in the end, probably be found to accord with the 

 breadth of the stratum of water of the temperature 

 they require. It is the warmer currents flowing 

 from the south northwards, and passing beneath 

 the cold waters of the arctic current, that originate 

 this distribution of temperature and animals in 

 depth. A very important fact is this — for, as we 

 know from observation, the animals of the depths 

 are members of the fauna of the Boreal or next 

 southern province ; whilst it is in the shallows, or 

 along the littoral and laminarian belts on the coast, 

 or in the colder upper waters, unfavourable as they 

 are to life, that we find the characteristic and pecu- 

 liar members of the Arctic province. The presence 

 of the former is, in all probability, due to their dif- 

 fusion northwards by the under current. The pau- 

 city of numbers of the marine creatures inhabiting 

 the higher zones may also be in part dependent on 

 the composition of the waters of the Arctic seas, for 

 their upper stratum is less salt than in seas more to 

 the south ; whilst the greater saltness of the under 

 layer, taken in connection with the exceeding clear- 

 ness of the waters, through which the bottom and 

 the shells upon it are plainly visible, even at a 

 depth of eighty fathoms, go far to favour the de- 



