295 



Of such works published subsequently to 1859, 

 several are monographic 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 ob- 

 servations and the ingenuity of the reasonings 

 which it records, or the prodigious mass of sub- 

 sequent 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 vegetable world. 



So far back as 1793, the wonderful work of 

 Sprengel had established, beyond any reasonable 

 doubt, the fact that, in a large number of cases, a 

 flower is a piece of mechanism the object of which 

 is to convert insect visitors into agents of fertilisa- 



