310 ABSENCE OF INTERMEDIATE VARIETIES 



formations in Europe, have of fcenest given rise, first to local 

 varieties and ultimately to new species ; and this again 

 would greatly lessen the chance of our being able to trace 

 the stages of transition in any one geological formation. 



It is a more important consideration, leading to the same 

 result, as lately insisted on by Dr. Falconer, namely, that 

 the period during which each species underwent modification, 

 though long as measured by years, was probably short in 

 comparison with that during which it remained without 

 undergoing any change. 



It should not be forgotten, that at the present day, with 

 perfect specimens for examination, two forms can seldom be 

 connected by intermediate varieties, and thus proved to be 

 the same species, until many specimens are collected from 

 many places; and with fossil species this can rarely be 

 done. We shall, perhaps, best perceive the improbability 

 of our being enabled to connect species by numerous, fine, 

 intermediate, fossil links, by asking ourselves whether, for 

 instance, geologists at some future period will be able to 

 prove that our different breeds of cattle, sheep, horses, and 

 dogs are descended from a single stock or from several abo- 

 riginal stocks ; or again, whether certain sea-shells inhabiting 

 the shores of North America, which are ranked by some con- 

 chologists as distinct species from their European represent- 

 atives, and by other conchologists as only varieties, are really 

 varieties, or are, as it is called, specifically distinct. This 

 could be effected by the future geologist only by his discov- 

 ering in a fossil state numerous intermediate gradations ; 

 and such success is improbable in the highest degree. 



It has been asserted over and over again, by writers who 

 believe in the immutability of species, that geology yields 

 no linking forms. This assertion, as we shall see in the 

 next chapter, is certainly erroneous. As Sir J. Lubbock 

 has remarked, " Every species is a link between other allied 

 forms." If we take a genus having a score of species, 

 recent and extinct, and destroy four-fifths of them, no one 

 doubts that the remainder will stand much more distinct 

 from each other. If the extreme forms in the genus hap- 

 pen to have been thus destroyed, the genus itself will stand 

 more distinct from other allied genera. What geological 

 research has not revealed, is the former existence of infi- 

 nitely numerous gradations, as fine as existing varieties, con- 

 necting together nearly all existing and extinct species. 

 But this ought not to be expected ; yet this has been 



