. Animal hormones; a comparative survey. Hormones. Fig. 3-13. Two ommatidia from the compound eye of the prawn, Palaemonetes, in longitudinal section to show pigment cells which change shape, (a) In Z), the ommatidium is shown with the pigment cells in the extreme dark-adapted position; in L, in the extreme light-adapted position. As in Fig. 3-12, the pigment in the distal retinal cells () surrounds the cone (con.) in the dark position, and the rhabdome (rh.) in the light. In L, the pigment in the proximal retinal cells (, not shown in D) has dispersed outwards from below the baseme
. Animal hormones; a comparative survey. Hormones. Fig. 3-13. Two ommatidia from the compound eye of the prawn, Palaemonetes, in longitudinal section to show pigment cells which change shape, (a) In Z), the ommatidium is shown with the pigment cells in the extreme dark-adapted position; in L, in the extreme light-adapted position. As in Fig. 3-12, the pigment in the distal retinal cells () surrounds the cone (con.) in the dark position, and the rhabdome (rh.) in the light. In L, the pigment in the proximal retinal cells (, not shown in D) has dispersed outwards from below the basement membrane (just out of the figure), (b) The same ommatidia with the pigment removed to show contractile fibres () in the distal retinal cells (). They are attached to a mass of accessory pigment (). In D, the fibres are relaxed in the dark-adapted position; in L, the fibres are contracted in the light. Most of the cell protoplasm and the nuclei () have moved inwards with the pigment, leaving only an attenuated distal cell process (). The nuclei of the proximal or retinula cells () remain stationary (from Welsh, 1930). diurnal rhythm that persists in constant darkness; but this is reduced or absent in continuous light. The rhythm can be induced experimentally to become out of phase with the time of solar daylight. About one-third of the dark-adapting hormone of the crab eyestalk is in the sinus gland, and two-thirds in the ''optic. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Jenkin, Penelope M. Oxford, New York, Pergamon Press
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Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjecthormones
