442 Life and Immortality. 



world has been geologically explored ; that only organic 

 beings of certain classes, at least in any great number, can be 

 preserved in a fossil condition ; that many species when 

 once formed never undergo any further change, but become 

 extinct without leaving any modified descendants ; that domi- 

 nant and widely-ranging species vary the most and the most 

 frequently, and that varieties are often at first only local, it 

 is not at all surprising that the discovery of intermediate 

 links to any considerable extent should not have been made. 

 Local varieties, as is well known, will not diffuse themselves 

 into other and distant localities until they have become 

 very much modified and improved, and when they have thus 

 diffused themselves, and are discovered in a geological forma- 

 tion, they will appear as if suddenly created there, and will 

 simply be ranked as new species. Besides, formations have 

 often been intermittent in their accumulation, and their dura- 

 tion has probably been shorter than the average duration of 

 specific forms. And as successive formations in most cases 

 are separated from each other by blank intervals of time of 

 considerable length, and as fossiliferous formations thick 

 enough to withstand future degradation can as a general 

 rule be accumulated only where much sediment is laid down 

 in the subsiding bed of the ocean, it follows that during the 

 alternate periods of elevation and of stationary level the 

 record will generally be blank or devoid of fossil remains. 

 During these latter periods there will doubtless be more 

 variability in the forms of life, and during the periods of 

 subsidence a greater amount of extinction. Now, as geology 

 plainly declares that each land has undergone great physical 

 changes, we have a right to expect that organic beings have 

 varied under nature in the same manner as they have varied 

 under domestication, and such have scientific study and 

 research found to be the case. And if there has been any 

 variability under nature, such a fact would seem unaccount- 

 able unless Natural Selection, or the Survival of the Fittest, 

 did not come into play. Upon the view that variations have 



