ITS EXTENT AND ITS MARINE FAUNA. 21 



and I was one of the nieniLers. We gradually extended our 

 dredging into deeper water until in 1867 we worked in 170 

 fathoms, about 35 miles in the ocean north-north-west of 

 Burra Firth Lighthouse, which is situated on the most northerly 

 rock of the Shetland Islands. This dredging had, at that time, 

 only been surpassed in European seas by Professor Michael Sars, 

 who published an account in 1868 of animals found by him 

 in from 200 to 450 fathoms, but this was in the sheltered fiords 

 of the Norwegian coast. 



The question that remains to be determined is : What are the 

 natural boundaries of the marine fauna of our own or of any 

 country? 1 answer that the boundary is the base-line of the 

 country or continent as it rests upon the bed of the ocean. 

 If we are to admit any deep-water marine fauna at all, no other 

 limit would appear to be reasonable. In shallow water we 

 have little difiiculty in defining certain zones. Thus there are : 

 (1) The Littoral Zone, i.e. the shore between high and low 

 water-mark, characterized by a fauna which in large measure 

 requires that a portion of its life should be spent under 

 atmospheric influence. (2) The Laminarian Zone, the region of 

 seaweeds, which afford nourishment for those animals which 

 live on a vegetarian diet. This zone may be said to extend 

 to 20 fathoms. (3) What Forbes denominated The Coralline 

 Zone, so named from its richness in Hydrozoic and Polyzoic 

 life, on the existence of which, again, a large number of animals 

 depend for their food. But beyond this no distinct line of 

 demarcation can be drawn, for although we may talk of the 

 Abyssal or Abysmal Region, there is no marked difference, at 

 any one depth, of the conditions of life, and hence there is 

 a gradual, and only gradual, intermixture of species. Therefore, 

 no one stated depth, such as that of 100 fathoms, can be taken 

 as the limit of a fauna. 



To return to my statement that the boundary of the marine 

 fauna is the base-line of the country or continent as it rests 

 upon the bed of the ocean. If a stone is placed in a basin, and 

 water poured in until almost the whole of the stone is covered, 

 that portion of it which is covered by the water right down 

 to the base where it rests on the basin is as much a portion 

 of the stone as the part uncovered. Just so with an island 

 or continent. The first thing therefore we have to determine 

 is at what depth the floor of the ocean is reached. Now if we 

 examine a chart of the North Atlantic we shall scarcely find 

 a place in which there is a depth of less than 1,500 fathoms 



