Development

Development, the spontaneous production of progressive diversity, is a universal phenomenon, dependent on what Mr. Herbert Spencer has termed the instability of the homogeneous. The influence of surrounding forces, varying in their co-operation or opposition, and the mere summation of effects from the repeated action of the same causes, tend to modify things, to make them unlike what went before. This process, acting under natural law, is development. It has been suggested that the substances we know as elements may have developed from some one primitive form of matter. "While the matter composing the Solar system has been assuming a denser form, it has changed from unity to variety of distribution. Solidification of the Earth has been accompanied by a progress from comparative uniformity to extreme multiformity. In the course of its advance from a germ to a mass of relatively great bulk, every plant and animal also advances from simplicity to complexity. The increase of a society in numbers and consolidation has for its concomitant an increased heterogeneity both of its political and its industrial organisation. And the like holds of all super-organic products - Language, Science, Art, and Literature." (Spencer.) Among the laws of this development we can only here allude to a few. Carl von Baer's principle of the parallelism of ontogeny, or the course of development of the individual, with phylogeny, or the course of development in the race, gave importance to the study of embryology as throwing light on the succession of organic forms in time. Darwin and Wallace showed the tendency of organisms to vary indefinitely from their original type; and Wallace has shown that individual variations may be of considerable extent. Cope's law of acceleration of development indicates the inheritance of characters arising by "spontaneous" variation at slightly earlier stages in the development of the individual in each successive generation. Dohrn, Lankester, and others have emphasised the fact that degeneration (q.v.), and even atavism or reversion, may and do occur as concomitants of a system of increasing diversity which may more often result in advance. The facts of variations occurring in several directions from one stock, and of the whole series having, as we often find among fossil forms, become extinct, militate against the idea of a necessary innate perfectibility in all organisms, such as was maintained by Lamarck and Nageli. The evidence of palaeontology (q.v.), though necessarily fragmentary, points clearly to a gradual development of organic life in its now infinite variety and in its marked geographical provinces.