cH.xx,vANTS AND PLANT-STRUCTURE 385 



worthy of being read there. I will here give some 

 passages from Darwin's reply, dated April i, 1869. 



" The facts which you state are extraordinary, 

 and quite new to me. If you can prove that the 

 effects produced by ants are really inherited, it 

 would be a most remarkable fact, and would open 

 up quite a new field of inquiry. You ask for my 

 opinion ; if you had asked a year or two ago I 

 should have said that I could not believe that the 

 visits of the ants could produce an inherited effect ; 

 but I have lately come to believe rather more in 

 inherited mutilations. I have advanced in opposi- 

 tion to such a belief, galls not being inherited. 

 After reading your paper I admit, Firstly, from the 

 presence of sacs in plants of so many families, and 

 their absence in certain species, that they must be 

 due to some extraneous cause acting in tropical 

 South America. Secondly, I admit that the cause 

 must be the ants, either acting mechanically or, as 

 may perhaps be suspected from the order to which 

 they belong, from some secretion. Thirdly, I 

 admit, from the generality of the sacs in certain 

 species, and from your not having observed ants in 

 certain cases (though may not the ants have paid 

 previous visits?), that the sacs are probably in- 

 herited. But I cannot feel satisfied on this head. 

 Have any of these plants produced their sacs in 

 European hot-houses ? Or have you observed the 

 commencement of the sacs in young and unfolded 

 leaves which could not possibly have been visited 

 by the ants? If you have any such evidence, I 

 would venture strongly to advise you to produce 

 it. ... 



VOL. II 2 C 



