On Sotne Interactions of Organisms. 9 



might be if the species dependent upon it did not oscil- 

 late, — and, the food being less, the average number of the 

 species itself must be smaller. Our problem is, therefore, 

 to determine how these innumerable small oscillations, 

 due to imperfect adjustment, are usually kept within 

 bounds, — to discover the forces and laws which tend to pre- 

 vent either inordinate increase or decrease of any species, 

 and also those by which widely oscillating species are 

 brought into subjection and reduced to a condition of pros- 

 perous uniformity. We may know in general that such 

 laws and forces are constantly at work, and that the ten- 

 dency of things is towards this healthful equilibrium, be- 

 cause we see substantially such an equilibrium widely 

 established and steadily maintained through long periods 

 of time, notwithstanding the great number and kaleido- 

 scopic variability of the forces by which each species is im- 

 pressed. But this idea will repay more detailed elucida- 

 tion. We will notice, first, some of the checks upon inju- 

 rious oscillations arising out of the laws of the individual 

 organism, and afterwards those which are brought to bear 

 upon it from without. 



It will at once be seen that, in any case, the maladjust- 

 ments possible are of only two kinds, — the rate of repro- 

 duction in the species must be either relatively too small 

 or relatively too great. If it be relatively too small, if 

 the species bring forth fewer young than could mature, on 

 the average, under existing circumstances, whatever may 

 be the oscillations arising, they will tend to disappear with 

 the disappearance of the species. The average numbers 

 of such a species being, in the most favorable event, less 

 than they might be, it will be at a certain disadvantage 

 in the general struggle for existence, — it will eventually 

 yield to some more prolific species with which it comes in 

 competition. If, for any reason, its rate of multiplication 

 be or become too high, the law of the antagonism between 

 individuation and genesis will constantly tend to bring it 

 wathin the proper limit. Reproduction being more active 

 than is necessary, the individual force and activity will 

 be less than it might be, — the species will be at a disad- 

 vantage in the search for food, and in all its other activi- 



