Animals manifestly enjoy excitement, and suffer from annul and may exhibit curiosity.

Everything in nature is the result of fixed laws.

The most important factor in survival is neither intelligence nor strength but adaptability.

Each organic being is striving to increase in a geometrical ratio . . . each at some period of its life, during some season of the year, during each generation or at intervals, has to struggle for life and to suffer great destruction . . . The vigorous, the healthy, and the happy survive and multiply.

We have happy days, remember good dinners.

Delight itself, however, is a weak term to express the feelings of a naturalist.

As man advances in civilization, and small tribes are united into larger communities, the simplest reason would tell each individual that he ought to extend his social instincts and sympathies to all members of the same nation, though personally unknown to him. This point being once reached, there is only an artificial barrier to prevent his sympathies extending to the men of all nations and races.