in many cases colors were useful to the organisms possessing them. Sprengel expressed his belief that the colors of flowers served to attract insects which aided in the fertilization of the seeds. Other observers showed that dull hues in animals might assist a persecuted species to escape from enemies, or a persecuting species to steal upon prey. Such views were at once utilized by the promoters of the celebrated "argument from design," who contended that these creatures were so made when created, the useful coloring being conclusive evidence of a designing intelligence on the part of the Creator. In those days all paths in the fields of science led to the domains of theology, where it was unsafe to 
Catocala Moth at Rest. wander without the guidance of a keeper appointed by the church. To this individual puzzling problems were easy of solution: "God intended it so, and who shall dare to question the actions of Infinity?" Natural phenomena were given supernatural explanations which were accepted in a way that seems incredible to us to-day. But gradually the law of parsimony in logic—the law which in this case directed that when a phenomenon can be explained in natural terms, we must not appeal to supernatural ones—became accepted, and reasons that had long held good were rejected as worthless. The hold of dogmatism and priestcraft upon science gradually relaxed as the church meddled less in secular matters and religion became an affair of the heart rather than of the intellect.
It is one of the triumphs of biology—the youngest of sciences—that she has already given an adequate explanation for the existence of most of the phases of animate color. We all now know that the colors of flowers exist, as Sprengel believed, to attract insects, and that insects are attracted to insure cross-fertilization—a fact of which Sprengel was not aware. All the world is familiar with accounts of mimicry—"the imposture of Nature"—as well as of protective and aggressive resemblance. Nearly every one has seen pictures of the kallima insect, which when in motion is a gaudy butterfly, and at rest becomes a dry and withered leaf; or of the various leaf insects and stick insects of the tropics. Many of us have seen in imagination the puff adder which Professor Drummond did not sit upon in the wilds of Africa, or have watched with Forbes the bird's-dropping
