46 EXPLANATIONS. 



necessary for the creation of the superior creatures. 

 And, if so, it undoubtedly is a powerful evidence 

 of such a theory of development as that which I 

 have presented. If not so, let me hear any equally 

 plausible reason for the great and amazing fact 

 that seas were for numberless ages destitute of 

 fish. I fix my opponents down to the considera- 

 tion of this fact, so that no diversion respecting 

 high mollusks shall avail them. But this is not all. 

 The Silurian is an age, as were several subsequent 

 ones, of only marine animals. It is now incon- 

 testable, from a few land-plants found in the Silu- 

 rians of America, and a fern leaf in our own, that 

 there was dry land ; yet no trace of a land animal 

 appears for ages afterwards. Moreover, though 

 we have now a pretty full development of the first 

 sub-kingdom, Radiata, we have but an imperfect 

 one of the two next — namely, the Articulata and 

 MoUusca. Not to speak of the utter absence of 

 fresh-water and land mollusks, and of such land 

 articulata as insects and spiders, we do not find 

 any decapodous Crustacea (crabs, &c.), though these 

 could have lived wherever other mollusks and 

 Crustacea could. In fact, it is a scanty and most 

 defective development of life ; so much so, that 

 Mr. Lyell calls it, par excellence, the Age of 



