Page:The Zoologist, 4th series, vol 5 (1901).djvu/366

338 of the deeper waters. The sight perception of fishes is clearly a phenomenon, of which we have practically the smallest information, and the scantiest imagination.

It is even probable, as Bernstein has proposed, that the perception of the external world is essentially an act of the mind, which has its seat in the cerebrum, and is connected with this organ; and, further, that the sensory organ, with its nervous connections, only affords the brain the material which it converts into a Sensory Perception. For it has been observed with Pigeons, that upon the removal of the cerebral hemispheres, in which state they may live for some time, they still possess a sensation of light, which penetrates the eye, and causes a contraction of the pupil; an action which can only be caused by the central organ of the optic nerve in the brain. But a comprehension of the objects seen—i.e. a true perception of the senses—is no longer possible to these animals. They behave like blind animals, run against every obstacle, and no longer possess the power of recognizing the objects seen as belonging to the external world.

If it is granted that the perception of the external world is essentially an act of the mind, and has its seat in the cerebrum of man, and that Pigeons are proved to have the same relation between their sight perceptions and the integrity of their cerebral hemispheres, then we cannot hesitate to apply the qualifying influence of difference in evolution of cerebral matter between man and other animals as largely modifying their power of equally appreciating by sight the shape, colour, and size of the different natural objects around them. We may therefore pause before concluding that the insectivorous mammal, bird, or reptile sees as we do the "protective" or "non-protective" shape and colouration of its prey, or that the bird to the insect, or the insect to the bird, appears to each, as both to ourselves. And so with all that we consider "warning colours," a great element of error may exist in our calculations, owing to a difference in the sense perceptions of the animals most clearly interested in the theory formulated.