294 THE ORIGIN OF SPECIES 



that no one doubts tliat tlicy arc of importance, yet 

 their use has not been, or has only recently been, as- 

 certained. As Bronn gives the length of the ears and 

 tail in the several species of mice as instances, though 

 trifling ones, of differences in structure which can be 

 of no special use, I may mention that, according to Dr. 

 Schobl, the external ears of the common mouse are sup- 

 plied in an extraordinary manner with nerves, so that 

 they no doubt serve as tactile organs; hence the length 

 of the ears can hardly be quite unimportant. We shall, 

 also, presently see that the tail is a highly useful pre- 

 hensile organ to some of the species; and its use would 

 be much influenced by its length. 



With respect to plants, to which, on account of 

 Nageli's essay, I shall confine myself in the follow- 

 in<r remarks, it will be admitted that the flowers of 

 orchids present a multitude of curious structures, which 

 a few years ago would have been considered as mere 

 morphological differences without any special function; 

 but they are now known to be of the highest impor- 

 tance for the fertilization of the species through the aid 

 of insects, and have probably been gained through natu- 

 ral selection. No one until lately would have imagined 

 that in dimorphic and trimorphic plants the different 

 lengths of the stamens and pistils, and their arrange- 

 ment, could have been of any service, but now we know 

 this to be the case. 



In certain whole groups of plants the ovules stand 

 erect, and in others they are suspended; and within the 

 same ovarium of some few plants, one ovule holds the 

 former and a second ovule the latter position. These 

 positions seem at first purely morphological, or of no 



