[Walter even gave the tortoises a mock-biological name, Machina speculatrix] because they illustrate particularly the exploratory, speculative behavi… - William Grey Walter

These models are of course so simple that any more detailed comparison between them and living creatures would be purely conjectural.

In any case there is an intense modern interest in machines that imitate life. The great difference between magic and the scientific imitation of life is that where the former is content to copy external appearance, the latter is concerned more with performance and behavior.

[E]xperiments with a simple little machine, designed to mimic certain elementary features of animal behavior... Consisting only of two vacuum tubes, two motors, a photoelectric cell and a touch contact, all enclosed in a tortoise-shaped 'shell, the model was a species of artificial creature which could explore its surroundings and seek out favorable conditions. It was named Machine speculatrix.