74 EVOLUTION [Chap. II 



Letter 33 therefore capable [of] and generally undergoing further de- 

 velopment. 



Is it not an extraordinary fact, the great difference in 

 position of the heart in different species of Cleodora ? ! I am 

 a believer that when any part, usually constant, differs con- 

 siderably in different allied species that it will be found 

 in some degree variable within the limits of the same species. 

 Thus, I should expect that if great numbers of specimens 

 of some of the species of Cleodora had been examined with 

 this object in view, the position of the heart in some of 

 the species would have been found variable. Can you aid 

 me with any analogous facts ? 



I am very much pleased to hear that you have not given 

 up the idea of noticing my cirripedial volume. All that 

 1 have seen since confirms everything of any importance 

 stated in that volume — more especially I have been able 

 rigorously to confirm in an anomalous species, by the 

 clearest evidence, that the actual cellular contents of the 

 ovarian tubes, by the gland-like action of a modified portion 

 of the continuous tube, passes into the cementing stuff: in 

 fact cirripedes make glue out of their own unformed eggs ! 2 



Pray believe me, 



Yours sincerely, 



C. Darwin. 

 I told the above case to Milne Edwards, and I saw he 

 did not place the smallest belief in it. 



Letter 34 To T. H. Huxley. 



Down, Sept. 2nd, [1854]. 



My second volume on the everlasting barnacles is at last 

 published, 3 and I will do myself the pleasure of sending you 

 a copy to Jermyn Street next Thursday, as I have to send 

 another book then to Mr. Baily. 



And now I want to ask you a favour — namely, to answer 

 me two questions. As you are so perfectly familiar with 

 the doings, etc., of all Continental naturalists, I want you 

 to tell me a few names of those whom you think would care 



1 A genus of Ptcropods. 



2 On Darwin's mistake in this point see Life and Letters, III., p. 2. 



3 A Monograph of the Sub-class Cirripcdia. II. The Balanidce, the 



Verrucida. Kay Society, 1854. 



