I recall the living Icthyophis, the curious burrowing salamander, which I once had the opportunity of observing in Ceylon. This is surprisingly like a worm in many regards, yet a mimic it can not be, since it could derive no profit from the resemblance, the worm being infinitely less protected than itself. If any mimicry could exist in this case it is clearly in the opposite direction, the worm mimicking the salamander, but this possibility is precluded since the mimicking form is infinitely more plentiful than the mimicked, and, most significant, neither form is apt to expose itself in a light where the resemblance would have any value. None the less the mutual resemblance is quite striking—in shape, proportions, size, color, annulation, movements, position of vent, etc. Yet we can only interpret it as due to parallelism. And if this is the case, may not parallelism, i. e., similarity in structures due to similarity in habits, not mere accidental resemblance, be taken as a further danger in interpretation.
For the rest we may query, as others have done, whether the importance of protective coloration and mimicry may not be still further diminished when we eliminate our anthropomorphic conception of the senses of the lower animals. For we may reasonably harbor the suspicion that colors and patterns, which to man seem protective, are by no means as valuable as protection against the keener and more specialized visual impressions of the lower animals. For just as "scent" perception in certain invertebrates, as in various moths, is immeasurably refined, far more so than we are in the habit of conceiving the scent-sense, so also there may have been developed a special sense for detecting the most subtle differences in color, texture, form in those animals which prey upon mimetic and protectively colored forms. Indeed, such a view is the less unreasonable when one considers the condition of the optic centers and end organs in those vertebrates, teleosts, reptiles, amphibia, birds, which have most to do with creatures in which protective coloration and mimicry is supposed to occur most abundantly. And it is not beyond the pale of possibility that the predatory forms have evolved habits in connection with sense-organs which would cause them to distinguish more promptly the protected forms than those having bright and obvious colors. It is in this direction that we have need of close observation and critical experiment.