MYSTEKIOUS FORMS OF LIFE. 71 



Modern evolution, which maintains such a descent, allows mil- 

 lions of years for the accomplishment of the transmutations; 

 but the diluvialists never claimed over five thousand years, and 

 resented the offer of geology to place more time at their disposal. 



If the relics buried in the rocks present undoubted diver- 

 gences from living forms, it must be because they lived in 

 other ages, and under different physical conditions from mod- 

 ern species. As there is now, so there must always have been, 

 some co-ordination or suitability between the conditions in 

 which species lived, and the structures, instincts, and capabili- 

 ties of the species. We are witnesses of this great prin- 

 ciple the adaptation of organism to environment. The Hippo- 

 potamus and the Elephant, dwellers in warm climates, are 

 almost naked. The White Bear and the Arctic Fox, dwellers 

 in the frigid zone, are densely clad in fur. , The Duck is im- 

 pelled by its instinct to the water; so its feet are webbed to 

 adapt it to movement in the water. These co-ordinations of 

 structure to environment or surroundings, are everywhere 

 seen, and possess extreme interest. Let me ask you, my 

 reader, to study out a great many other examples. 



Now, during the long history of rock-accumulation, there 

 must have taken place very great changes in the conditions 

 of the world. This may be inferred from the fact that some 

 changes are taking place before our eyes; and also from the 

 fact, which we must admit, that the ocean was once universal, 

 but is now interrupted by wide continental expanses which 

 deflect the winds and the currents of the sea, and modify the 

 climates of many regions. It might thus be inferred before- 

 hand, that the populations of the world have shown a corre- 

 spondence with the changing conditions of the world. If the 

 physical world has improved if it has undergone a progres- 

 sion from some cruder condition to the present, then the pop- 

 ulations of the world have progressively improved ; and we 

 shall find the records of this improvement in the fossil re- 

 mains of those populations, as we hunt for them in strata 

 farther and farther from the surface that is, farther and far- 

 ther removed in their origin from the present time. 



