The birds, for example, indulge in elaborate and beautiful evolutions of a playful sort at the mating season.
2.

It follows from their instinctive character that animal plays are peculiar to the species which perform them.

We find series of sports peculiar to dogs, others to cats, and so on through all the species of the zooelogical garden, whether the creatures be wild or tame.

Each shows its species as clearly by its sportive habits as by its shape, cry, or any other of what are called its "specific" habits.

This is important not only to the zooelogist, as indicating differences of evolution and scale of attainment, environment, etc., but also to the psychologist, as indicating differences of what we may call animal temperament.