272 EVOLUTION [CHAP. IV 



Letter 192 the astronomical chapter, 1 as I am as ignorant as a pig on this 

 head. I shall require some days to read what has been sent. 

 I have just read Chapter IX., 2 and like it extremely ; it all 

 seems to me very clear, cautious, and sagacious. You do not 

 allude to one very striking point enough, or at all viz., the 

 classes having been formerly less differentiated than they now 

 are ; and this specialisation of classes must, we may conclude, 

 fit them for different general habits of life as well as the 

 specialisation of particular organs. 



P. i62. 3 I rather demur to your argument from Cetacea : 

 as they are such greatly modified mammals, they ought to 

 have come in rather later in the series. You will think me 

 rather impudent, but the discussion at the end of Chapter IX. 

 on man, 4 who thinks so much of his fine self, seems to me too 

 long, or rather superfluous, and too orthodox, except for the 

 beneficed clergy. 



Letter 193 To V. Cai'US. 



The following letter refers to the 4th edition of the Origin, 1866, 

 which was translated by Professor Carus, and formed the 3rd German 

 edition. Carus continued to translate Darwin's books, and a strong 

 bond of friendship grew up between author and translator (see Life and 

 Letters, III., p. 48). Nageli's pamphlet was first noticed in the 5th 

 English edition. 



Down, Nov. 2 rst, 1866. 



. . . With respect to a note on Nageli 5 I find on considera- 

 tion it would be too long ; for so good a pamphlet ought to 



1 Principles of Geology, by Sir Charles Lyell ; Ed. X., London, 

 1867. Chapter XIII. deals with "Vicissitudes in Climate how far 

 influenced by Astronomical Causes." 



2 Chapter IX, " Theory of the Progressive Development of Organic 

 Life at Successive Geological Periods." 



3 On p. 163 Lyell refers to the absence of Cetacea in Secondary rocks, 

 and expresses the opinion that their absence " is a negative fact of great 

 significance, which seems more than any other to render it highly impro- 

 bable that we shall ever find air-breathers of the highest class in any of 

 the Primary strata, or in any of the older members of the Secondary 



series." 



4 Loc. tit., pp. 167-73, " Introduction of Man, to what extent a Change 

 of the System." 



5 " Entstehung und Begriff der Naturhistorischen Art," an Address 

 given before the Royal Academy of Sciences at Munich, March 28th, 

 1865. See Life and Letters, III., p. 50, for Mr. Darwin's letter to the 

 late Prof. Nageli. Carl Wilhelm von Nageli (1817-91) was born at 



