For example, when reading in a geology text-book about the stratification of the earth in a certain region, draw the parts described and label them according to the description.

In this broad sense, it may with truth be said, that all living animals, and all those dead faunae which geology reveals, are bound together by an all-pervading unity of organisation, of the same character, though not equal in degree, to that which enables us to discern one and the same plan amidst the twenty different segments of a lobster's body.