464 



MB. W. E. HOYLE ON THE DEEP-WATER 



For this purpose use must be made of the distributional notes 

 appended to each species in the list. According to this infor- 

 mation the species fall into three categories. The first contains 

 those which range from Scandinavia to the Mediterranean, or 

 even more widely still ; these may be termed, for the present 

 purpose, " Wide-spread " species. The second consists of those 

 forms which are common to the Arctic and Scandinavian waters, 

 and hence may be termed " Northern;" whilst the third is made 

 up of species which may be called " Southern," as they extend 

 to the Mediterranean or the African coast. 



The following Table shows the numbers of species of the 

 various classes of animals which belong to each of these cate- 

 gories : — 





Wide-spread 

 Species. 



Northern 

 Species. 



Southern 

 Species. 





23 



17 



2 





4 



5 





Mollusca and 1 

 Brachiopoda ... J 



46 



22 



3 





20 



5 



1 





32 



41 



5 



Vermes 



3 



3 







10 



13 



2 





9 



4 



9 



Totals 



147 



110 



22 



From these figures it appears that the major part of the fauna 

 is composed of species which are dispersed more or less widely 

 over the north temperate regions of the globe, whilst the smaller 

 half is very unequally divided between the northern and southern 

 species, the former being five times as numerous as the latter. 

 In only one division of animals (the Coelenterata) do the southern 

 forms predominate over th^ northern, and this sub kingdom has 

 been hitherto very inadequately investigated in the Clyde area. 



The depth of 20 fathoms as limiting what might be considered 

 the deep-water fauna in the Clyde sea-area was selected not 

 from any preconceived idea as to its significance, but because it 

 was convenient for practical purposes, and because it was appli- 

 cable to all the lochs, the extreme depth of the Gareloch, which 



