LIFE AND MECHANISII. 31 in fact, find that, when placed in circumstances not previously met with by them, and therefore not provided for, they would fail to act so as to attain the end which conduces, under these circumstances, to maintaining the organism in action. This, however, is just what these cells do not do ; since in whatever way the injury to the limb may be varied, they adapt their behaviour to the circum- stances of the case, and attain the end of reproducing the limb. In the process of healing, then, we meet with facts similar to those already discussed in the case of the earth- worm. The two cases which I have taken are of course only isolated examples of phenomena which prevail more or less throughout the whole organic world, and to which pheno- mena as a whole the above analysis may be made to apply. That analysis enables us to conclude that the purposive behaviour displayed in the attainment by organisms of such ends as the reproduction of a newt's limb, or the stopping up of an earthworm's burrow, cannot be due to the mere action of neuro- muscular or intracellular mechanisms. This conclusion does not, however, carry with it an assertion of the existence within the organism of phenomena altogether different from those outside of it. It is quite intelligible that a stone falls back again to the earth, in whatever direction it may have been propelled in the air. The attraction of the earth overcomes the force w r hich propels the stone away, in whatever direction that force may be. The propelling force may be varied in direction to any extent, yet the stone reaches the earth with certainty. Now if we do not make the unmeaning assumption that an intelligence which is supernatural influences, nevertheless, the physical world, it is necessary to suppose that, in the case of the class of phenomena which we have been con- sidering, there must be some explanation similar to that of the behaviour of the stone. When an earthworm stops up its hole in spite of such disturbing influences as were intro- duced by Darwin, its behaviour is analogous to that of a stone in reaching the ground in whatever direction it may have been originally propelled. And in order to render the movements of the worm intelligible we must suppose it to be in some way influenced by a force of attraction. But it is at least clear that no direct force of this sort guides the worm in its movements relatively to the burrow and the materials used ; and the like is true of other instances of purposive action. This, however, does not exclude the existence of a connecting force which acts in an indirect and
