ANNUAL ADDRESS OF THE PRESIDENT. xXLiUt 
of change is that many are in a definite direction, which is gradually 
becoming known. This general course of change is denominated 
Evolution, and the term must be defined. 
Evolution is progress in systemization. It must be noted that 
not all changes are progressive; some are retrogressive. It is only 
progressive change that is here called evolution; retrogressive change 
is dissolution. As the term is here used, a System is an assemblage 
of interdependent parts, each arranged in subordination to the 
whole so as to constitute an integer. Evolution may therefore be 
defined in another way. It is progress in differentiation by the 
establishment of unlike parts, and in the integration of these parts 
by the establishment of interdependence. Dissolution is retrogres- 
sion by the lapsing of integration through the destruction of inter- 
dependence, and the lapsing of differentiation through the loss of 
heterogeneity in parts. 
EVOLUTION IN THE PHYSICAL KINGDOM. 
Under the kinematic hypothesis, which embraces the ethereal and 
nebular hypotheses, portions of discrete matter have been segregated 
to be combined and aggregated. The process precedent to evolu- 
tion, then, is combination and aggregation, by which substauces 
and integers are produced. 
Whatever may be the fate of the explanation of the origin of 
substances and aggregates through the kinematic and concomitant 
hypotheses, the fact remains that such bodies exist, and the evolu- 
tion of matter, as it is hereafter dealt with, starts from this point. 
Given substances and aggregates as they are known to exist in 
nature, and given changes which they are known to undergo, it is 
proposed to point out by what methods evolution is attained. 
The terms substance and aggregate have been used as distin- 
guishing two orders of combination. It should be noted that they 
cannot be clearly demarcated. Substances are composed of homo- 
geneous, non-interdependent parts, but this homogeneity is never 
absolute, and some slight degree of interdependence may always be 
discovered. Aggregates, on the other hand, are composed of hetero- 
geneous, interdependent parts, but degrees of heterogeneity and 
interdependence appear. Combination is the bringing together of 
dissociated matter; and it is in the combinations, separations, and 
re-combinations of matter that evolution appears. 
