214 LOUIS AOASSIZ. 



about science, and that my spirit is not irre- 

 sponsive to a noble encouragement such as 

 you have given me. 



You will have received my letter from Carls- 

 ruhe. Could I only tell you all that I have 

 since thought and observed about the history 

 of our earth's development, the succession of 

 the animal populations, and their genetic clas- 

 sification ! It cannot easily be compressed 

 within letter limits; I will, nevertheless, at- 

 tempt it when my lectures make less urgent 

 claim upon me, and my eyes are less fatigued. 

 I should defer writing till then were it not 

 that to-day I have something of at least out- 

 side interest to announce. It concerns the in- 

 closed letter received to-day. (The offer of 

 a professorship at Heidelberg.) Should you 

 think that I need not take it into considera- 

 tion, and you have no time to answer me, let 

 me know your opinion by your silence. I will 

 tell you the reasons which would induce me 

 to remain for the present in Neuchatel, and I 

 think you will approve them. First, as my 

 lectures do not claim a great part of my time 

 I shall have the more to bestow on other work ; 

 add to this the position of Neuchatel, so favor- 

 able for observations such as I propose making 

 on the history of development in several classes 



