2oS Z.6V/.V .lu.lSS/Z. [CHAP, xxin. 



cal fatigue. The effort had been too great, and the 

 strain upon his health beyond reason. When among 

 pupils it was impossible to restrain him. He must 

 teach. Teaching was as natural to him as breath- 

 ing to others; but after his illness of 1870, he was 

 obliged to exert himself to deliver his lectures, and 

 it was often painful to see him forcing his voice 

 through his over-fatigued throat. His throat was the 

 weak point in his herculean frame. However, October, 



1873, found him again at his post in his Museum, and 

 he began a course of lectures on the radiates from 

 their first appearance until the present time. At the 

 same time he dictated to Mrs. Agassiz an article for 

 the " Atlantic Monthly," on " Evolution and Perma- 

 nence of Type," which did not appear until January, 



1874, after his death. As it is his last production, it 

 may be taken as " Louis Agassiz's Scientific Will " ; and 

 a few quotations will serve to show his strong convic- 

 tions on the most exciting of all natural history subjects. 



The law of evolution, so far as its working is understood, is a 

 law controlling development and keeping types within appointed 

 cycles of growth, which revolve forever upon themselves, returning 

 at appointed intervals to the same starting-point, and repeating 

 through a succession of phases the same course. These cycles 

 have never been known to oscillate or to pass into each othn ; 

 indeed, the only structural differences known between individuals 

 of the same stock are monstrosities or peculiarities pertaining to 

 sex, and the latter are as abiding and permanent as the type itself. 

 Taken together the relations of sex constitute one of the mnM 

 obscure and wonderful features of the whole organic world, all the 

 more impressive for its universality. . . . 



Under the recent and novel application of the terms " evolution " 

 and "evolutionists," we are in danger of forgetting the only 



