. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 418 ANNALS OF THE SOUTH AFRICAN MUSEUM C 20" hours Fig. 10. Temperature changes over 24 hours in midsummer at Blouberg. temperature temperature at 300 mm. temperature at 450 mm. surface humidity of more than 90% at 75 mm below the surface. The upper 75 mm of sand is frequently dried out during the day by sun and wind, but as no animals are in this layer during the daylight hours, this presents no danger. At night with the drop in temperature, spray from the sea together with any dew deposi
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 418 ANNALS OF THE SOUTH AFRICAN MUSEUM C 20" hours Fig. 10. Temperature changes over 24 hours in midsummer at Blouberg. temperature temperature at 300 mm. temperature at 450 mm. surface humidity of more than 90% at 75 mm below the surface. The upper 75 mm of sand is frequently dried out during the day by sun and wind, but as no animals are in this layer during the daylight hours, this presents no danger. At night with the drop in temperature, spray from the sea together with any dew deposi- tion keeps the air close to the sand almost saturated with water vapour, thereby preventing desiccation. LIGHT Tylos capensis and T. granulatus It is not possible for sunlight to penetrate more than 25 mm below the surface of the sand; sunlight would thus have very little direct influence on the animals. When exposed to sunlight, the animals rapidly burrow into the sand, and can be said to be strongly negatively photosensitive. When not feeding, both species react to both white and coloured light by becoming immobile, but bright white light has little immediate effect on feeding animals. EXTRANEOUS FACTORS During week-ends, both areas studied form part of a popular beach, and are often continuously trampled. This does not seem to have any effect on the nightly emergence of the 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 South African Museum. Cape Town : The Museum
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
