CHAPTER VII

THE MEANING OF EVOLUTION 245

Argument.--If we assume the existence of an evolutionary process, the results of morphology, embryology, and palæontology ought to enable us to trace the directions followed during this process. But these results are still so uncertain that they indicate only a few main lines of transformism. Phylogenetic trees are largely conjectural in matters of detail. Evolution has resulted in the establishment of several dominant groups of organisms--the metatrophic bacteria, the chlorophyllian organisms, the arthropods, and the vertebrates. Each of these groups displays certain characters of morphology, energy-transformation, and behaviour; and a certain combination of characters is concentrated in each of the groups. But there is a community of character in all organisms which have arisen during the evolutionary process. The transformation of kinetic into potential energy is characteristic of the chlorophyllian organisms. The utilisation of potential energy, and its conversion into the kinetic energy of regulated bodily activity, by means of a sensori-motor system, is characteristic of the animal. The bacteria carry to the limit the energy-transformations begun in the tissues of the plants and animals. Immobility and unconsciousness characterise the plant, mobility and consciousness the animal. Animals indicate two types of actions--intelligent actions and instinctive actions. Instinctive activity involves the habitual exercise of modes of action that have been inherited. Intelligent activities involve the exercise of modes of action that are not inherited, but which are acquired by the animal during its own lifetime, and are the results of perceptions which show the animal that its activity is relative to an outer environment.