Here comes in an upward step indeed.

"A world that only cared for eggs becomes," as Professor Drummond observes in his _Ascent of Man,_ "a world that cares for its young." The first faint trembling dawn, or at least shadowing forth, of a moral life, in the care of the strong for the weak, makes itself seen, which henceforth becomes as pervasive an element in Nature as the fierce struggle for existence in which the weak are destroyed by the strong.[20] In the bird--till now "the free queen of the air," living at her own wild will, suddenly fettered and brooding on her nest, and covering her helpless young with her tender wings--we see some faint image of the Divine tenderness.

In the ceaseless toil of both the parent birds from morning till night to fill the little gaping throats we begin to feel the duty of the strong to serve and protect the weak; and in the little hen partridge, still clinging to her nest, when the flash of the scythe is drawing nearer and nearer, till reapers have told me they have feared the next sweep of the scythe might cut off her head, we see more than a shadow of that mother's love which is stronger than death.

And when we pass lastly to the highest order of animals, the mammalia, we find them named after the mother's function of giving suck to her young from her own breast.

They are no longer matured in an external egg, but are borne in her own body till they are able to breathe, and seek their nourishment from her, and then they are born so helpless that, as with kittens and puppies, they often cannot even see.
In this higher order of animals nothing can exceed the devotion of the mother to her young in their helpless infancy.