Ch. II] BARNACLES. 39 



was lost by illness. On this account I went in 1848 for some 

 months to Malvern for hydropathic treatment, which did me 

 much good, so that on my return home I was able to resume 

 work. So much was I out of health that when my dear father 

 died on November 13th, 1848, I was unable to attend his 

 funeral or to act as one of his executors. 



My work on the Cirripedia possesses, I think, considerable 

 value, as besides describing several new and remarkable forms, 

 I made out the homologies of the various parts — I discovered 

 the cementing apparatus, though I blundered dreadfully about 

 the cement glands — and lastly I proved the existence in certain 

 genera of minute males complemental to and parasitic on the 

 hermaphrodites. This latter discovery has at last been fully 

 confirmed ; though at one timo a German writer was pleased 

 to attribute the whole account to my fertile imagination. The 

 Cirripedos form a highly varying and difficult group of species 

 to class ; and my work was of considerable use to me, when I 

 had to discuss in the Origin of Species the principles of a 

 natural classification. Nevertheless, I doubt whether the work 

 was worth the consumption of so much time. 



From September 1854 I devoted my whole time to arranging 

 my huge pile of notes, to observing, and to experimenting in 

 relation to the transmutation of species. During the voyage of 

 the Beagle I had been deeply impressed by discovering in the 

 Pampcan formation great fossil animals covered with armour 

 like that on the existing armadillos ; secondly, by the manner 

 in which closely allied animals replace one another in pro- 

 ceeding southwards over the Continent ; and thirdly, by the 

 South American character of most of the productions of the 

 Galapagos archipelago, and more especially by the manner in 

 which they differ slightly on each island of the group ; none of 

 the islands appearing to be very ancient in a geological sense. 



It was evident that such facts as these, as well as many 

 others, could only be explained on the supposition that species 

 gradually become modified ; and the subject haunted me. But 

 it was equally evident that neither the action of the surrounding 

 conditions, nor the will of the organisms (especially in the case 

 of plants) could account for the innumerable cases in which 

 organisms of every kind are beautifully adapted to their habits 

 of life — for instance, a woodpecker or a tree-frog to climb trees, 

 or a seed for dispersal by hooks or plumes. I Lad always been 

 much struck by such adaptations, and until these could be 

 explained it seemed to me almost useless to endeavour to prove 

 by indirect evidence that species have been modified. 



After my return to England it appeared to me that by 



