. The biology of dragonflies (Odonata or Paraneuroptera). Dragon-flies. 128 THE NERVOUS SYSTEM [CH. into six main parts, which will be dealt with, in order, from the compound eye inwards to the procerebral lobe. 1. The layer of fost-retinal fibres, or terminal anastomosis (pr). Each ommatidium (p. 141) rests upon the fenestrate membrane (/), and sends through it delicate nerve-fibres, which at once collect together in bundles. These bundles quickly pass into a narrow layer of nerve-cells, which form with them a plexus. From this. op ic ajgi^einc^ g'pf^'^ "^^ cf tn Fig. 58. through ri
. The biology of dragonflies (Odonata or Paraneuroptera). Dragon-flies. 128 THE NERVOUS SYSTEM [CH. into six main parts, which will be dealt with, in order, from the compound eye inwards to the procerebral lobe. 1. The layer of fost-retinal fibres, or terminal anastomosis (pr). Each ommatidium (p. 141) rests upon the fenestrate membrane (/), and sends through it delicate nerve-fibres, which at once collect together in bundles. These bundles quickly pass into a narrow layer of nerve-cells, which form with them a plexus. From this. op ic ajgi^einc^ g'pf^'^ "^^ cf tn Fig. 58. through right optic ganglion and eye of Austrolestes ledn Selys ( x 50), with key below. The arrows indicate the part represented in the key. Explana- tion in text. Original. plexus the bundles emerge irregularly, being separated from one another by large and thin-walled tracheae {tr'). They next enter another small layer of nerve-cells, forming a second plexus, lying just outside the ganglionic plate. All this complex structure is called the terminal anastomosis. The portion lying nearest to the fenestrate membrane is heavily charged with black pigment,. 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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