Masterpieces of Science 



happened is of such a character as to render 

 the assumption that they did not happen in 

 the highest degree improbable ; and the question 

 I now have to deal with is, whether evidence 

 in favour of the evolution of animals of this 

 degree of cogency is, or is not, obtainable from 

 the record of the succession of living forms 

 which is presented to us by fossil remains. 



Those who have attended to the progress of 

 palaeontology are aware that evidence of the 

 character which I have denned has been pro- 

 duced in considerable and continually-increas- 

 ing quantity during the last few years. Indeed, 

 the amount and the satisfactory nature of that 

 evidence are somewhat surprising, when we 

 consider the conditions under which alone we 

 can hope to obtain it. 



It is obviously useless to seek for such evi- 

 dence, except in localities in which the physical 

 conditions have been such as to permit of the 

 deposit of an unbroken, or but rarely interrupted, 

 series of strata through a long period of time; 

 in which the group of animals to be investigated 

 has existed in such abundance as to furnish 

 the requisite supply of remains; and in which, 

 finally, the materials composing the strata are 

 such as to insure the preservation of these re- 

 mains in a tolerably perfect and undisturbed 

 state. 



It so happens that the case which, at present, 

 most nearly fulfils all these conditions is that 

 of the series of extinct animals which culminates 

 102 



