RECENT PROGRESS OF NATURAL SCIENCE. 601 



suits of the same powers of Nature which are actively at work on the 

 earth at the present time ; and that, moreover, the gradual but ever 

 active powers of water, of air, and of chemical change, have perhaps 

 had a greater share in accomplishing these transformations than the 

 fierce heat of subterranean masses of lava. The explorers of the buried 

 remains of plants and animals show it to be impossible that all life in 

 those geological formations could have been destroyed simultaneously, 

 for many species are common at several stages ; in particular, many 

 existing animals and plants reach far back into the primitive world. 

 Man himself could be shown to have been contemporary with many 

 extinct species of plants and animals, and therefore his age on the 

 earth must be extended back to an indefinite period. Man was wit- 

 ness to that inundation which buried the plains of the old and the new 

 world under the waves of the sea of ice. Even in the immediately 

 preceding period, when the sub-tropical elephant, rhinoceros, and 

 hippopotamus, disported themselves in the lignite woods of Middle 

 Europe, have traces of mankind been found. Only in the most recent 

 times has a foundation been laid for the prehistoric records of man- 

 kind, by means of which we may be able to obtain a kuowledge of the 

 state of civilization, weapons, implements, and dwellings, of that primi- 

 tive race. 



No book of recent times, Dr. Cohn thinks, has influenced to such 

 an extent the aspects of modern natural science, as Charles Darwin's 

 work " On the Origin of Species," the first edition of which appeared 

 in 1859. For, even to so late a period, was the immutability of spe- 

 cies believed in ; so long was it accepted as indubitable that all the 

 characteristics which belong to any species of plants and animals 

 were transmitted unaltered through all generations, and were under 

 no circumstances changeable ; so long did the appearance of new fauna 

 and flora remain one of the impenetrable mysteries of science. He who 

 would not believe that new species of animals and plants, from the 

 yeast-fungus to the mammalia, had been crystallized parentless out of 

 transformed matei'ials, was shut up to the belief that in primeval time 

 an omnipotent act of creation, or, as it may be otherwise expressed, a 

 power of Nature, at present utterly unknown, interfered with the regu- 

 lar progress of the world's development ; yea, according to the re- 

 searches of D'Orbigny and Elie de Beaumont, twenty-seven different 

 acts of creation must have followed each other previous to the appear- 

 ance of man but, after that, no more. It Avas Darwin who lifted 

 natural science out of this dilemma, by advancing the doctrine that 

 the animals and plants of the late geological eras no more appeared all 

 at once upon the scene, than those of the preceding epochs simultane- 

 ously and suddenly disappeared ; on the contrary, these are the direct 

 descendants of former species, which gradually in the course of an ex- 

 ceedingly long period, through adaptation to altered conditions of life, 

 through the struggle for existence, through natural and sexual selec- 



