Charles Darwin. 457 



modus operandi of Natural Selection. Such are the two 

 volumes on "Domesticated Animals and Cultivated Plants," 

 illustrating Variation, Inheritance, Reversion, Interbreeding, 

 &c. ; the volume on the " Descent of Man, and Selection in 

 Relation to Sex," — which extended the hypothesis to its logi- 

 cal limits, — and that "On the Expression of the Emotions in 

 Man and the Lower Animals," published in 1872, which may 

 be regarded as the last of this series. Since then Mr. Darwin 

 appears to have turned from the highest to the lower forms of 

 life, and to have entered upon the laborious cultivation of new 

 and special fields of investigation, which, although prosecuted 

 on the lines of his doctrine and vivified by its ideas, might 

 seem to be only incidentally connected with the general argu- 

 ment. But it will be found that all these lines are convergent. 

 Nor were these altogether new studies. The germ of the three 

 volumes upon the Relation of Insects to Flowers and its far- 

 reaching consequences, is a little paper, published in the year 

 1858, " On the Agency of Bees in the Fertilization of Papilio- 

 naceous Flowers, and on the Crossing of Kidney Beans:"' the 

 6ret edition of the volume on "The various Contrivances by 

 which Orchids are Fertilized by Insects" appeared in 1862, thus 

 forming the second volume of the whole scries; and the two 

 volumes "On the Effects of Cross- and Self-Fertilization in the 

 Vegetable Kingdom," and "The Different Forms of Flowers 

 on Plants of the same Species," which, along with the new 

 edition of "The Fertilization of Orchids.'" were all published in 

 1876 and 1877, originated in two or three remarkable papes 

 contributed to the Journal of the Linnean Society in 1862 and 

 1863, but are supplemented by additional and protracted ex- 

 periments. The volume on "Insectivorous Plants," and the 

 noteworthy conclusions in respect to the fundamental unity, 

 »nd therefore common source, of vegetable and animal life, 

 grew out of an observation which the author made in the sum- 

 mer of 1860, when he -was surprised by finding how large a 

 number of insects were caught by the leaves of the common 

 'Sun-dew {Drosrra rotnmlijnlia), on a heath in Sussex." Almost 

 everybody had noticed this; and one German botanist (Roth), 

 just a hundred years ago, had observed and described the 

 l consequence of the capture. But noth- 



