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 Whales, Porpoises, Dolphins.—As the absurd mistake is sometimes made of confusing whales with fish, the pupil may compare them in the following respects: eggs, nourishment of young, fins, skin, eyes, size, breathing, temperature, skeleton (Figs. 209, 379, and 397).

(see Fig. 351).

Porpoises and dolphins, which are smaller species of whales, live near the shore and eat fish. Explain the expression "blow like a porpoise." They do not exceed five or eight feet in length, while the deep-sea whales are from thirty to seventy-five feet in length, being by far the largest animals in the world. The size of the elephant is limited by the weight that the bones and muscles support and move. The whale's size is not so limited.

The whale bears one young (rarely twins) at a time. The mother carefully attends the young for a long time. The blubber, or thick layer of fat beneath the skin, serves to retain heat and keep the body up to the usual temperature of mammals in spite of the cold water. It also serves, along with the immense lungs, to give lightness to the body.