PDF - Wallace Online

142 NATURAL SELECTION vnsupervision and direct interference of the Creator, andcannot possibly be explained by the unassisted action of anycombination of laws. Now, Mr. Darwin's work has for itsmain object to show that all the phenomena of living things,all their wonderful organs and complicated structures, theirinfinite variety of form, size, and colour, their intricate andinvolved relations to each other, may have been producedby the action of a few general laws of the simplest kind, lawswhich are in most cases mere statements of admitted facts.The chief of these laws or facts are the following:1. The Law of Multiplication in Geometrical Progression.All organised beings have enormous powers of multiplication.Even man, who increases slower than all other animals, couldunder the most favourable circumstances double his numbersevery fifteen years, or a hundredfold in a century. Manyanimals and plants could increase their numbers from ten toa thousandfold every year.2. The Law of Limited Populations. The number of livingindividuals of each species in any country, or in the wholeglobe, is practically stationary; whence it follows that thewhole of this enormous increase must die off almost as fastas produced, except only those individuals for whom room ismade by the death of parents. As a simple but strikingexample, take an oak forest. Every oak will drop annuallymany thousands of acorns, but till an old tree falls not oneof the millions of acorns produced can grow up into an oak.They must die at various stages of growth.3. The Law of Heredity, or Likeness of Offspring to theirParents. This is a universal, but not an absolute law. Allcreatures resemble their parents in a high degree, and in themajority of cases very accurately; so that even individualpeculiarities, of whatever kind, in the parents, are almostalways transmitted to some of the offspring.4. The Law of Variation. This is fully expressed by thelines :" No being on this earthly ball,Is like another, all in all. "Offspring resemble their parents very much, but not wholly-each being possesses its individuality. This " variation "itself varies in amount, but it is always present, not only in