VIII. 



THE DEEP-SEA FAUNA. 



It is vain to inquire what animals and plants could have 

 lived in the primordial ocean. We can only conjecture, if we 

 adopt the speculations of Mallet regarding the conditions of 

 the ocean, that they must have been capable of bearing an 

 intense degree of heat, and probably inhabited a mass of boil- 

 ing; mud. 



Whole classes of animals and plants live only in the water, 

 and cannot subsist elsewhere : water penetrates all their tissues, 

 and from it they take the elements needed for their growth. 

 Animals living in salt water, with very few exceptions, die in 

 fresh water, probably from the lack of soluble salts.^ There 

 are vast numbers of animals whose function seems to be the 

 distribution of the soluble salts which have from time imme- 

 morial been swept into the sea. Globigerinae, pteropods, mol- 

 lusks, echinoderms, corals, and sponges, all distribute over the 

 floor of the ocean, in the form of shells or solid calcareous skel- 

 etons, the lime and silica which they have derived from the sea- 

 water. 



In an atmosphere saturated with moisture, Crustacea could live 

 under moist stones and bark. Lichens as well as many infuso- 

 ria, which when dry remain inert, but are resuscitated by moist- 

 ure again, may have formed the principal elements of the fauna, 

 and have survived durinor the transition from the older marine 

 to a very moist climate, or one resembling the climates of the 

 present day. Similar adaptations may have led to the gradual 

 change of marine shells into terrestrial types. In fishes proper 



^ Sharks are known to inhabit Lake on the shores of northern Brazil extend 



Nicaragua and the fresh waters of some far up the Amazons, and some hydroids 



of the larger rivers of India ; many marine flourish in fresh water, 

 fishes, selachians, and cetaceans common 



