xxi 



unfrequently, months of suffering rendered work of any kind 

 impossible. Even Darwin's remarkable tenacity of purpose and metho- 

 dical utilisation of every particle of available energy could not have 

 enabled him to achieve a fraction of the vast amount of labour he 

 got through, in the course of the following forty years, had not the 

 wisest and the most loving care unceasingly surrounded him from the 

 time of his marriage in 1839. As early as 1842, the failure of health 

 was so marked that removal from London became imperatively 

 necessary; and Darwin purchased a house and grounds at Down, a 

 solitary hamlet in Kent, which was his home for the rest of his life. 

 Under the strictly regulated conditions of a valetudinarian exist- 

 ence, the intellectual activity of the invalid might have put to shame 

 most healthy men ; and, so long as he could hold his head up, there 

 was no limit to the genial kindness of thought and action for all 

 about him. Those friends who were privileged to share the intimate 

 life of the household at Down have an abiding memory of the cheerful 

 restfulness which pervaded and characterised it. 



After mentioning his settlement at Down, Darwin writes in his 

 Autobiography : — 



" My chief enjoyment and sole employment throughout life has 

 been scientific work ; and the excitement from such work makes me, 

 for the time, forget, or drives quite away, my daily discomfort. 1 

 have, therefore, nothing to record during the last of my life except the 

 publication of my several books." (I, p. 79.) 



Of such works published subsequently to 1859, several are mono- 

 graphic discussions of topics briefly dealt with in the ' Origin,' which, 

 it must always be recollected, was considered by the author to be 

 merely an abstract of an opus majus. 



The earliest of the books which may be placed in this category, 

 ' On the Various Contrivances by which Orchids are Fertilised by 

 Insects,' was published in 1862, and whether we regard its theoretical 

 significance, the excellence of the observations and the ingenuity of 

 the reasonings which it records, or the prodigious mass of subsequent 

 investigation of which it has been the parent, it has no superior in 

 point of importance. The conviction that no theory of the origin of 

 species could be satisfactory which failed to offer an explanation of 

 the way in which mechanisms involving adaptations of structure and 

 function to the performance of certain operations are brought about, 

 was, from the first, dominant in Darwin's mind. As has been seen, 

 he rejected Lamarck's views because of their obvious incapacity to 

 furnish such an explanation in the case of the great majority of 

 animal mechanisms, and in that of all those presented by the vege- 

 table world. 



So far back as 1793, the wonderful work of Sprengel had estab- 

 lished, beyond any reasonable doubt, the fact that, in a large number 



c 2 



