322 Professor Edward Forbes on the Light thrown on 



is the case. The geological application of this fact, of a zero 

 of life in the ocean, is evident. All deposits formed below 

 that zero, will be void, or almost void, of organic contents. 

 The greater part of the sea is far deeper than the point zero ; 

 consequently, the greater part of deposits forming, will be 

 void of organic remains. Hence we have no right to infer that 

 any sedimentary formation, in which we find few or no traces 

 of animal life, was formed either before animals were created, 

 or at a time when the sea was less prolific in life than it now 

 is. // might have been formed in a very deep sea. And that 

 such was the case in regard to some of our older rocks, such 

 as the great slates, is rendered the more probable, seeing that 

 the few fossils we find in them, belong to tribes which, at pre- 

 sent, have their maximum in the lowest regions of animal life, 

 such as the Brachiopoda, and Pteropoda, of which, though free 

 swimmers in the ocean, the remains accumulate only in very 

 deep deposits. The uppermost deposits, those in which or- 

 ganic remains would be most abundant, are those most liable 

 to disappear, in consequence of the destroying action of denud- 

 ation. The great and almost nonfossiliferous strata of Sca- 

 glia,' which form so large a part of the south of Europe and of 

 Western Asia, were probably, for the most part, formed be- 

 low the zero of life. The few fossils they contain, chiefly 

 nummulites, correspond to the foraminifera which now abound 

 mostly in the lowest region of animals. There is no occa- 

 sion to attribute to metamorphic action the absence of traces 

 (rf living beings in such rocks. 



III. The number of northern forms of animals and plants is 

 not the same in all the zones of depths but increases either 

 positively, or by representation, as we descend. — The associa- 

 tion of species in the littoral zone is that most characteristic 

 of the geographical region we are exploring ; but the lower 

 zones have their faunas and floras modified by the presence 

 of species which, in more northern seas, are character- 

 istic of the littoral zones. Of course, this remark applies only 

 to the northern hemisphere ; though, from analogy, we may 

 expect to find such inversely the case also in the southern. 

 The law, put in the abstract, appears to be, that parallels in 



