780 LOUIS AGASSIZ, 



their power for evil and for good upon living 

 beings. But there is, nevertheless, nothing 

 more striking in the whole book of nature 

 than the power shown by types and species to 

 resist physical conditions. Endless evidence 

 may be brought from the whole expanse of 

 land and air and water, showing that identical 

 physical conditions will do nothing toward the 

 merging of species into one another, neither 

 will variety of conditions do anything toward 

 their multiplication. One thing only we know 

 absolutely, and in this treacherous, marshy 

 ground of hypothesis and assmnption, it is 

 pleasant to plant one's foot occasionally upon 

 a solid fact here and there. Whatever be the 

 means of preserving and transmitting proper- 

 ties, the primitive types have remained perma- 

 nent and unchanged, — in the long succession 

 of ages, amid all the appearance and disap- 

 pearance of kinds, the fading away of one 

 species and the coming in of another, — from 

 the earliest geological periods to the present 

 day. How these types were first introduced, 

 how the species which have successively repre- 

 sented them have replaced one another, — 

 these are the vital questions to which no an- 

 swer has been given. We are as far from 

 any satisfactory solution of this problem as 



