In the indigo snake, a pattern of undulating lines on the surface of the skin, formed by the junction of rows of cells, acts as a two-dimensional optical diffraction grating to produce the play of colors. The distance between repetitive units of the pattern measured from observations made with an electron microscope are in agreement with those found by spectrometric analysis.

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The attenuation of ultrasonic compressional waves in the nematic liquid crystal, N-(p-ethoxybenzylidene}-pbutylaniline (EBBA), has been measured as a function of frequency, temperature, and the angle between an aligning magnetic field and the direction of wave propagation. The results are interpreted in terms of theories of nematic liquid crystals based on hydrodynamics and micropolar continuum mechanics. It is shown that the correct expression for the attenuation anisotropy can also be derived from Leslie's theory of anisotropic fluids. It was found that shear viscosity coefficients had the usual exponential dependence on inverse temperature with an activation energy of 10 kcallmole whereas volume viscosity coefficients had a more complex temperature dependence. The attenuation of compressional waves in the unoriented nematic phase is compared with that of the oriented crystal.

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