OBJECTIONS TO THE THEORY OF NATURAL SELECTION 173 



according to Dr. Schobl, the external ears of the common mouse 

 are supplied 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 prehensile 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 following remarks, it will be admitted 

 that the flowers of the orchids present a multitude of curious struc- 

 tures, 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 importance for the fertilization 

 of the species through the aid of insects, and have probably been 

 gained through natural selection. No one until lately would have 

 imagined that in dimorphic and trimorphic plants the different 

 lengths of the stamens and pistils, and their arrangement, 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 physiological signification; but Dr. Hooker informs me 

 that within the same ovarium, the upper ovules alone in some 

 cases, and in others the lower ones alone are fertilized; and he 

 suggests that this probably depends on the direction in which 

 the pollen-tubes enter the ovarium. If so, the position of the 

 ovules, even when one is erect and the other suspended within 

 the same ovarium, would follow the selection of any slight devia- 

 tions in position which favored their fertilization, and the produc- 

 tion of seed. 



Several plants belonging to distinct orders habitually produce 

 flowers of two kinds — the one open, of the ordinary structure, the 

 other closed and imperfect. These two kinds of flowers sometimes 

 differ wonderfully in structure, yet may be seen to graduate into 

 each other on the same plant. The ordinary and open flowers can 

 be intercrossed; and the benefits which certainly are derived from 

 this process are thus secured. The closed and imperfect flowers 

 are, however, manifestly of high importance, as they yield with 

 the utmost safety a large stock of seed, with the expenditure of 

 wonderfully little pollen. The two kinds of flowers often differ 

 much, as just stated, in structure. The petals in the imperfect 

 flowers almost always consist of mere rudiments, and the pollen- 

 grains are reduced in diameter. In Ononis columnar five of the 



