Once outside of the water, these animals gradually adapted themselves more and more to life on land. Some became reptiles (creatures who crawl like lizards) and they shared the silence of the forests with the insects. That they might move faster through the soft soil, they improved upon their legs and their size increased until the world was populated with gigantic forms (which the hand-books of biology list under the names of Ichthyosaurus and Megalosaurus and Brontosaurus) who grew to be thirty to forty feet long and who could have played with elephants as a full grown cat plays with her kittens.