LAST PUBLIC LECTURE. Y81 



if development theories had never been dis- 

 cussed." 



In conclusion, he sketches the plan of these 

 articles. " I hope in future articles to show, 

 first, that, however broken the geological rec- 

 ord may be, there is a complete sequence in 

 many parts of it, from which the character of 

 the succession may be ascertained ; secondly, 

 that, since the most exquisitely delicate struc- 

 tures, as well as embryonic phases of growth 

 of the most perishable nature, have been pre- 

 served from very early deposits, we have no 

 right to infer the disappearance of types be- 

 cause their absence disproves some favorite 

 theory ; and, lastly, that there is no evidence 

 of a direct descent of later from earlier spe- 

 cies in the geological succession of animals ' 



This paper contained the sentence so often 

 quoted since, " A physical fact is as sacred as 

 a moral principle. Our own nature demands 

 from us this double allegiance." This ex- 

 pressed the secret of his whole life. Every 

 fact in nature was sacred to him, as part of 

 an intellectual conception expressed in the 

 history of the earth and the beings living 

 upon it. 



On the 2d of December, he was called to 

 a meeting of the Massachusetts Board of 



