. The biology of dragonflies (Odonata or Paraneuroptera). Dragon-flies. 106 THE ALIMENTARY AND EXCRETORY SYSTEMS [CH. arranged into equal numbers of larger and smaller kinds, placed alternately. These are known as major and minor folds respectively. Thus the gizzard has a distinct radial symmetry. Sixteen appears to have been the original number, eight being major folds, and eight minor. A reduction to eight, and then to four major folds took place in some forms. In the Anisoptera, four is the regular number, except in the Petalurinae, where there are eight. In the Zygoptera, sixteen is the us
. The biology of dragonflies (Odonata or Paraneuroptera). Dragon-flies. 106 THE ALIMENTARY AND EXCRETORY SYSTEMS [CH. arranged into equal numbers of larger and smaller kinds, placed alternately. These are known as major and minor folds respectively. Thus the gizzard has a distinct radial symmetry. Sixteen appears to have been the original number, eight being major folds, and eight minor. A reduction to eight, and then to four major folds took place in some forms. In the Anisoptera, four is the regular number, except in the Petalurinae, where there are eight. In the Zygoptera, sixteen is the usual number, but there are many cases of reduction to eight. A B. m K#^A^-^^^W^V^/-/. 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 Tillyard, Robin John, 1881-1937. Cambridge [Eng. ] : University Press
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