VI.] INTRODUCTION. cix 



diterranean telegraph- cable, and with the same results ; 

 and the forthcoming work of Dr. Wallich on " The 

 North- Atlantic Sea-bed " will doubtless contain some 

 important observations on the existence and forms of 

 animal life at extreme depths in the Ai'ctic Sea. 



Although it does not come strictly within the scope 

 of the present treatise, I cannot help contrasting the 

 fecundity of the sea with the comparative sterility of the 

 land, as regards animal life — if we consider the countless 

 shoals which swarm in every part of the ocean and 

 thickly cover its bed, and that the air, even in its lower 

 zones, is almost lifeless. The lines in the 12th Canto of 

 the ^ Faerie Queene ' seem to corroborate this idea, al- 

 though not so intended by the poet : — 



" O what an endlesse worke have I in hand, 



To count the seas abundant progeny, 

 Whose fruitfull seede farre passeth those in land, 



And also those which wonne in th' azure sky ! 



For much more eath to tell the starres on hy, 

 Albe they endless seeme in estimation, 



Then to recount the seas posterity : 

 So fertile be the flouds in generation, 

 So huge their numbers, and so numberlesse their nation. 



Witnesse th' exceeding fry which there are fed. 

 And wondrous sholes which may of none be red." 



Geological relations. — In local lists of Mollusca, and 

 even in more elaborate works on this subject, it has been 

 the custom to state that the habitat of certain species is 

 restricted to " calcareous soils,^^ " oolitic formations," 

 "limestone," "chalk," "trap," and other strata. I believe, 

 however, that mineralogical conditions have very little 

 to do with the habitat of any of the Mollusca, nor with 

 their comparative abundance or scarcity in any locality, 

 except so far as food, moisture, or shelter, as well as the 

 secretion of their shells, is concerned. Such conditions 



