Abstract
LONDON Royal Society, January 25. A. ZOOND and J. EYRE. Studies in reptilian colour response. (1) The bionomics and physiology of the pigmentary activity of the chameleon. In strong diffuse daylight chameleons become dark on a black background and pale on a white one. Blind animals darken in the light. This response depends upon the integrity of spinal reflex arcs. The time relations of these responses have been determined. The threshold for the retinal photoreceptors is lower than for the dermal ones. In weak light the white background response is reversed, the animals becoming dark. Low temperatures above 0 ° C. have no effect upon the normal response of chameleons to darkness. A theory of nervous coordination is developed. It is suggested that the ‘daily rhythm’ of colour changes may be interpreted in terms of the white background response in strong and weak light, without reference to temperature. A. WOLSKY and J. S. HUXLEY: The structure and development of normal and mutant eyes in Qam-marus chevreuxi. The eyes of ‘eye-colour mutants’ (‘red’, ‘no-white’, etc.) differ from normals only in pigmentation and not in structure. The eyes of eye-structure mutants (‘albino’, ‘colourless’) are markedly deficient as compared with normal. For the development of normal eyes, the results of Schatz (1929) are confirmed. The differentiation and growth of the optic tract (not previously studied in Gammarus) is centrifugal in time: the medulla externa and lamina ganglionaris are at first small, but eventually constitute a large and distinct protuberance. In the eye-structure mutants the adult optic tract is comparable with the early embryonic stage of normals. The structure of albino and colourless eyes can be formally explained in terms of (a) a rate-gene causing a delay in differentiation of the organs (optic tract and eye-mass) derived from the primary optic disc; (6) a graded distribution of the inhibitory effect caused by this delay; and (c) possibly, the consequent absence of a formative stimulus normally exerted by the optic tract upon the differentiation of the eye proper. J. NEEDHAM, C. H. WADDINGTON, and DOROTHY M. NEEDHAM: Physico-chemical experiments on the amphibian organiser. The induction of a secondary embryonic axis in amphibian gastrulse can be accomplished by the implantation of (a) cell-free extracts of the neurula, (6) ether and petrol-ether extracts of the neurula, (c) adult amphibian tissues, (d) ether extracts of adult amphibian viscera. A distinction is made between two factors in induction; the production of an embryonic axis as such, which is called evocation; and the determination of the regional, for example, antero-posterior, character of that axis, which is called individuation. The evocator is probably a definite chemical substance soluble in ether and petrol-ether.
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Societies and Academies. Nature 133, 186–188 (1934). https://doi.org/10.1038/133186a0
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DOI: https://doi.org/10.1038/133186a0