Page:The Zoologist, 4th series, vol 3 (1899).djvu/389

Rh that truth may exist between the two antagonists, for it seems certain we have not yet all the explanations of these mimetic disguises, and discussion may well precede a universal dogma of its causation. Because a phenomenon is frequent in nature, it is not necessarily universal. For instance, the metamorphosis in the early lives of Frogs is an observation of so general a nature as to indicate a constant law; but a land Frog in the Solomon Islands (Rana opisthodon) lays very large eggs in the crevices of rocks, and from these emerge fully-developed Frogs. We join issue with Prof. Tyler when he states, "Natural science does not deal in demonstrations, it rests upon the doctrine of probabilities; just as we have to order our whole lives according to this doctrine." This is a cardinal doctrine in natural and apologetic theology, but is the very antithesis of science, natural or otherwise. The man who orders his whole life on probabilities will probably arrive at the conclusion that hope is a very good breakfast, but a most indifferent dinner. A "science" based on probabilities may turn out to be a new system founded on contradictions.

Prof. Herdman, in speaking of the colours of Nudibranchs and their probably protective character, forcibly observes that we cannot gauge the problem by observing the animals in a museum-jar, or as illustrated in a book, or on the wall. "In order to interpret correctly the effect of their form and colours, we must see them alive and at home, and we must experiment upon their edibility or otherwise in the tanks of our biological stations." Such a course would doubtless give many positive and many negative results, confirming in many cases the theory—if it is still to called but a theory—of mimicry, and preventing many hasty and erroneous conclusions in other cases, where mimicry is only a suggestion, and much discredit is brought to the argument. The "law of evidence" might with advantage be studied