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 influence 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 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 importance for the fertilisation 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