INTRODUCTION. v 
<^ce of geology tmdS t0 Sh °' V ‘ hat tWS affl “ ity 13 mt mira ' Sal; the 1™**°“ is - what is 
and’™ Way Tm ‘° « 7 ‘"f ^ thS m * Ure ° f these for “ s is though analysis 
val v ofTZ ° r ^ them ' ^ Wha ‘ are •»*' A vast 
i ' f y of organisms of every shade and degree, and this variety of form not only 
r r h : s “; nto “ time - * - th " 
that as far bark 5 “ e reC0K, - shU a » almost endless variety-showing, beyond all question, 
organic portion of tb “f S °F readl ’ WhateTe1 ' be tbe duration of that period, the 
seme ° f the sur& ee of the globe, throughout its stages of progression has nre- 
1 ™ ri ;! ty ° f f T mS - FUrther : aS “ efet > « ha - ‘he fact of ’universal 
lutelv id i' eS ' iU 1S> tbat . n0 two individuals of any species can be held to be abso- 
rhe e ^ ' Ca ( r "! :iy assume this; for it is a natural deduction from what we see to be 
to h e a "', t '"? * , e hlgber forms, and, as far as we have any means of testing, it has proved 
a!Zt th V° Wer): “/ *“ differences vary in degree and in kind. Lastly, norivith 
TZf W , r°n , Vane ‘ y ’ indWdua,s ° f the same st ”ek return their identity to 
™£nt ~ r; ,- We r aWe 40 t "“ th<3m ’ “ d ’ afto a >™dred generations, 
On this we ha T . ‘ nCtl0ns fro “ theIr ancestors than they do from their contemporaries. 
On thi we have tangible points of comparison to start from ; for the bones of the Egyptian 
ZT “ “eh 6 mStaa ° e ’ ““ ° W ° f hntterflies and illustrated works on mtT- 
cultiZon of°Z r T anCe ’ C °'n q “ ite aSWide “ intOTal as We baTe assumed “hoao. The 
tions if any ancilnt 7" “ Chl “ a W ° Ul<l C ° Ver thousands instead of hundreds of genera- 
ChZe aL Z 1 P r T eX ‘ aat ’ WMCh " < " lite P ° SSible am0 ''« * L the 
vidual variation is looked 77 f “ tUIe ^ ‘ br ° W “ Ught 0n the sub j ect ' The f ao‘ of indi- 
how are we to define the 6,1" ffi “ mamStay ° f the hypothesis of modified descent; but 
period we have uuoted anZ ’”“ y ” U ' Ufy over even the short 
its identity and that not a o' 7 ' ’+ I 1 " 011 &n extent tllat ea ch species is able to retain 
possession of different dia’ "V “a ^ “ f Wielies of descent becoming settled in 
° , dl , ffe , le ”‘ diagnostic characteristics can be adduced. The ground taken that 
these indna dual differences multiplying in the direction most advantageous to the species 
ght to produce permanent alterations, is merely a deduction. The facts before us thomdi 
excessively limited in extent, tend to show that they do not produce permanent alterations 
inferred that species are so produced, because it is found possible to conceive that they 
. ««U U so produced, and that if so produced the process w ould fit in with a grZ and 
comprehensive theory; but it is impossible to avoid the admission that, as far as we know 
m actual proof positive, species are not produced by this process or by any other • and it is 
yet unproven that new species are in the course of formation at all, though of th sTere ” 
many possible indications. b theie aie 
h ZT regaid 1° tllG bel ! ef ln the lrnm utability of species, the strongest objection seems to 
and ultim P f ient l eVldence furnished by geology of the successive rise, prevalence, 
1 • -, d 6 PX mctl0n °b many genera. This objection even in the present crude state of 
geological research seems formidable, and must become more so from day to day as fresh dis- 
