LAWS OF MULTIPLICATION. 263 



respectively destructive or preservative of race ? How is the alternate excess of 

 one or other rectified ? A self-sustaining balance must exist ; the alternate 

 predominance of each force must initiate a compensatory excess of the other ; 

 how is this to be explained ? 



When favorable circumstances cause any species to become unusually 

 numerous, an immediate increase of destructive influences, passive as well as 

 active, takes place ; competition becomes keener and enemies more abundant, 

 and conversely. Yet this is not the sole, much less the permanent, means of 

 establishing a balance ; nor does it explain either the differences in the rate of 

 fertility and mortality, or the adaptation of one to the other. This minor adjust- 

 ment in fact implies a major one. 



The forces preservative of race were seen above to be two, — power to 

 maintain individual life, and power to generate the species. Now, in a species 

 which survives, given the forces destructive of race as a constant quantity, those 

 preservative of race must be a constant quantity also ; and, since the latter are 

 two, the individual plus the reproductive, these must vary inversely, one must 

 decrease as the other increases. To this law every species must conform, or 

 cease to exist. Let us restate this at greater length. A species in which self- 

 preservative life is low, and in which the individuals are accordingly rapidly 

 overthrown in the struggle with the destructive forces, must become extinct, 

 unless the other race-preservative factor be proportionally strengthened, — 

 unless, that is to say, its reproductive power become proportionally great. On 

 the other hand, if both preservative factors be increased, if a species of high 

 self-preservative power were also endowed with powers of multiplication beyond 

 what is needful, such success of fertility, if extreme, would cause sudden 

 extinction of the species by starvation, and if less extreme, and so effecting a 

 permanent increase of the numbers of the species, would next bring about such 

 intenser competition, such increased dangers to individual life, that the great 

 self-preservative power would not be more than sufficient to cope with them. 



In short, then, we have reached the a priori principle, that in races which 

 continuously survive, in which the destructive forces are balanced by the 

 preservative ones, there must be an inverse proportion between the power to 

 sustain individual life and the power to produce new individuals. But what is 

 the physiological explanation of this adjustment, and how has it arisen in 

 process of evolution ? Spencer has elsewhere enlarged upon the proposition, 

 which we have already illustrated, that genesis in all its forms is a process of 

 disintegration, and is thus essentially opposed to that process of integration 

 which is one element of individual evolution. The matter and energy supplied 

 for the young organism represent so much loss for the parent ; while, conversely, 

 the larger the amount of matter and energy consumed by the functional actions 

 of the parent, the less must be the amount remaining for those of the offspring. 

 The disintegration which constitutes genesis may be complete or partial, and in 

 the latter case the parent, having reached considerable bulk and complexity 

 before reproduction sets in, may survive the process. In the same way, 

 individual evolution may be expressed in bulk, in structure, in amount or 

 variety of action, or in combinations of these; yet, in any case, this progress of 

 each individuality must correspondingly retard the establishment of the new 

 ones. 



While in the first portion of the argument, then, it was shown that a species 

 can not be maintained unless self-preservative and reproductive power vary 

 inversely, it is now evident that, irrespective of an end to be subserved, these 

 powers can not do other than vary inversely, and the one a priori principle is 



