LOWER SILURIAN FOSSILS. 39 



And, as I have also remarked, there is a rapidity 

 of generation amongst the lower animals which 

 may well suggest something like that " rush of 

 life," which, if we were to judge from British 

 strata alone, would seem to have taken place in 

 the early seas. But there is no need for putting 

 any of these speculative answers to the objection 

 into requisition, while there is a preliminary ques- 

 tiou to be answered. Does the lowest band of 

 the English lower Silurians indicate, beyond 

 all question, the point of time at which animal 

 life commenced upon our planet r Are we quite 

 sure that cephalopoda were among the first of all 

 earth's living creatures? Far from it. It has 

 only been ascertained that certain comparatively 

 small cephalopods are found as far down as any 

 other animals of inferior organization at certain 

 spots in Wales and Cumberland. Ar\Tien we re- 

 member that, in modem seas, certain kinds of 

 such animals haunt special places suitable for 

 their subsistence — that we may have Crustacea 

 and mollusks exclusively at one place, and radiata 

 I as corals and zoophytes) at some other, not per- 

 haps far distant, but different with respect to depth 

 or some other circumstance — we can conceive 



