1 874.] ANTS. 191 



[Sir Charles Lyell's reply to the above letter must have 

 been one of the latest that my father received from his old 

 friend, and it is with this letter that the last volume of 

 Lyell's published correspondence closes.] 



C. Darwin to Aug. For el. 



& 



Down, October 15, 1874. 



My DEAR Sir, — I have now read the whole of your admir- 

 able work * and seldom in my life have I been more in- 

 terested by any book. There are so many interesting facts 

 and discussions, that I hardly know which to specify ; but I 

 think, firstly, the newest points to me have been about the 

 size of the brain in the three sexes, together with your sugges- 

 tion that increase of mind-power may have led to the sterility 

 of the workers. Secondly about the battles of the ants, and 

 your curious account of the enraged ants being held by their 

 comrades until they calmed down. Thirdly, the evidence of 

 ants of the same community being the offspring of brothers 

 and sisters. You admit, I think, that new communities will 

 often be the product of a cross between not-related ants. 

 Fritz Miiller has made some interesting observations on this 

 head with respect to Termites. The case of Anergates is 

 most perplexing in many ways, but I have such faith in the 

 law of occasional crossing that I believe an explanation will 

 hereafter be found, such as the dimorphism of either sex and 

 the occasional production of winged males. I see that you 

 are puzzled how ants of the same community recognize each 

 other ; I once placed two (F. rufci) in a pill-box smelling 

 strongly of asafcetida and after a day returned them to their 

 homes ; they were threatened, but at last recognized. I 

 made the trial thinking that they might know each other by 



* < 



Les Fourmis de la Suisse,' 4to, 1874. 



