In the words of Mr. Mivart it may be stated thus:
1. “Every kind of animal and plant tends to increase in numbers in a geometrical proportion.
2. “Every kind of animal and plant transmits a general likeness with individual differences to its offspring.
3. “Every individual may present minute variations of any kind in any direction.
4. “Past time has been practically infinite.
5. “Every individual has to endure a very severe struggle for existence, owing to the tendency to geometrical increase of all kinds of animals and plants, while the total animal and vegetable population (man and his agency excepted) remains almost stationary.
6. “Thus, every variation of a kind tending to save the life of the individual possessing it, or to enable it more surely to propagate its kind, will in the long run be preserved, and will transmit its favorable peculiarity to some of its offspring, which peculiarity will thus become intensified till it reaches the maximum degree of utility. On the other hand, individuals presenting unfavorable peculiarities will be ruthlessly destroyed. The action of this law of ‘natural selection’ may thus be well represented by the convenient expression, ‘survival of the fittest.’”
Now as to the series of facts which this theory throws light upon. Here they are as enumerated by Mr. Mivart. It explains:
1. Some singular facts “relating to the geographical distribution of animals and plants; as, for example, on the resemblance between the past and present inhabitants of different parts of the earth’s surface.
2. “That often, in adjacent islands, we find animals closely resembling and appearing to represent each other; while, if certain of these islands show signs of more ancient separation, the animals inhabiting them exhibit a corresponding divergence.