AND THE FISH THEREOF. 25 



how the larva of a Patella crossed the fathomless gulf between Finmark and 

 Greenland. It is a strong saying, but not said without a meaning, that the 

 existence of Alexander may have been determined by the migration of the 

 shell-fish. If I am right in my interpretation, we acquire a clue to the 

 origin of the peculiar physical conformation of the world as it is, and to the 

 disposition of those geographical arrangements upon which the development 

 of nations and characters of men in a great measure depend." 



ZONE VII. is that of the greatest depths, extending from 45 to 75 

 fathoms ; limestone springs rise here and there ; effect of light reduced to a 

 minimum; pressure at 60 fathoms, 12*26 atmospheres ; average temperature 

 52 F. ; difference of extreme temperatures 5 F., and change very gradual. 



The characteristic species are the Polyps Aglaophccnia myriophylhun, and 

 Semalaria lendigera; the bivalves, Pec ten glaber, Avicula tarentina, Venus 

 ovata, and Venus fasciata, and the univalve, Turritella quadricarinata, which 

 ends the short list. 



VERTEBRATES. 



The distribution of the Vertebrates is much more extended than that of 

 the forms hitherto described ; their division by horizontal regions is to a 

 certain extent practicable, but the limits are not nearly so well defined as is 

 the case with the Invertebrates. 



They are divided into two very distinct classes, viz. : — 



1. The Sedentary class of fishes, composed of those which are bound 

 to given limits, both horizontal and vertical ; these being determined by the 

 temperature or composition of the water, the depth, the nature of the bed 

 or the adjacent land, or the quality of their food. This class, which is also 

 called Shore fishes, is subdivided into what I shall term : — 



(a) The Rovers?- which hover about within given limits, suitable to 

 their particular predilections. 



1 I consider these divisions the most appropriate rendering of what Dr. Lorenz terms (a), 

 Grundschwarmer ; (b), Grundstete. 



E 



