With the introduction of steam-locomotion and the improvement of roads, however, riding has become to a large extent a sport, rather than a necessity.
- Diagram of Natural Locomotion of a Snake.
To Anthozoa - this group abandoned its power of adult locomotion by swimming.
Swimming is perhaps the commonest mode of locomotion, but numerous forms have taken to creeping or walking, and the robber-crab (Birgus latro) of the Indo-Pacific islands even climbs palm-trees.
The great problems involved in the study of geographical distribution must therefore be based mainly upon the other classes, both vertebrate and invertebrate, which, moreover, enjoy less great facilities of locomotion than the birds.