of animals? If Teufelsdröckh reduced society to a theory of clothes, it would seem that many advocates of Mimicry represent nature by a theory of masks. We observe a strong similarity between an animal and its environment, or between one which we believe possesses a quality procuring immunity from attack, and another in which that quality is absent, and we conclude that the resemblance or mimicry is equally observable by other creatures. Surely an element of error is present in this deduction. Is our world as we see it—and thus can only imagine it—the same in actual identity as that known by the sense cognitions of all animal life? If, as has been ably remarked, the universe contained only blind and deaf beings, it is impossible for us to imagine but that darkness and silence should reign everywhere.[1] If, on the other hand, we allow—as surely we ought—variation to exist in sense perceptions, as it undoubtedly does in the structure of sense organs, then, without leaving this planet, we may well understand that there are "other worlds than ours." Even in homology and variation, as Bateson has observed, "we have allowed ourselves to judge too much by human criterions of difficulty, and we have let ourselves fancy that nature has produced the forms of life from each other in the ways which we would have used, if we had been asked to do it."[2] Our knowledge of the sense organs in the lower animals is still very imperfect, and sometimes erroneous. Thus Weismann, in his lecture on the "Retrogressive Development in Nature," delivered in 1866, refers to the "Cæcilians, tropical worm-like or snake-like Amphibians, living underground," as having "lost not only the sense of sight, but that of hearing also." When this lecture was translated and published in this country a few years later, the author added a footnote, that "Recent researches have shown us that these animals not only possess a complete auditory apparatus, but that it is even more perfect than in other Amphibia"; and he adds, as a justification for the statement on which he founded his former conclusions, that "Up to the present time our knowledge of the auditory organ of Cæcilia has been founded upon the statements of two excellent observers, Professors Retzius and Wiedersheim; but the material at their
