Page:The Zoologist, 4th series, vol 1 (1897).djvu/563

Rh has published in the October number of our American contemporary 'The Auk' a communication on "Directive Coloration of Birds." The main thesis is that birds when sitting are protectively coloured; and when flying, directively. To illustrate this point an example is taken from mammals. "The common jack rabbit when squatting under a sage-bush is simply a sage-grey lump without distinctive colour or form. Its colour in particular is wholly protective, and it is usually accident rather than sharpness of vision which betrays the creature as it squats. But the moment it springs it is wholly changed. It is difficult to realize that this is the same animal. It bounds away with erect ears, showing the black and white markings on their back and under side. The black nape is exposed, the tail is carried straight down, exposing its black upper part surrounded by a region of snowy white; its legs and belly show clear white, and everything that sees it is plainly notified that this is a jack rabbit. The coyote, the fox, the wolf, the badger, &c, realize that it is useless to follow; the cottontail, the jumping rat, the fawn, the prairie dog, &c, that it is needless to flee; the young jack rabbit, that this is its near relative, and the next jack rabbit that this may be its mate. And thus, though incidentally useful to other species at times, the sum total of all this clear labelling is vastly serviceable to the jack rabbit, and saves it much pains to escape from real or imaginary dangers."

another theory on the method of evolution! Mr. Stuart Jenkins has sent us a pamphlet on the "Origin of Vertebrates," reprinted from the 'Medical Age,' and published at Detroit, Michigan. The author commences with an expression of sympathy with Lord Salisbury's well-known utterances at the Oxford meeting of the British Association, and a belief in the fact—never denied—"that Darwin has not said the last word in regard to evolution." He also fortifies his proposition with the equally well-known views of Huxley on non-fertility between hybrids. The new theory, which is of course inevitable, is "that the divergence of the vertebrates from the lower type was caused by the parasitic implantation of one organism of the ganglionic type upon another, the implanted organism giving rise to the cerebro-spinal nerve system and internal skeleton." The brochure evidently requires more study than we have been able to afford to render this proposition clear. We read that "utility has cut but an insignificant part in structural evolution, which has been brought about entirely by modifications of the cerebro-spinal parasite due to variation of nutrition." This theory of Parasitism we must own we fail to adequately understand, and therefore apologise for representing it by a perhaps obscure digest.