There is a small endosternite in the hinder portion of the cephalothorax under the alimentary canal.
The vascular system is not completely understood. The heart is a very long, narrow, dorsal tube, extending almost the entire length of the animal, and possessing eight pairs of ostia, two in the cephalothorax and six in the abdomen. It gives off an anterior and a posterior vessel, the latter apparently a vein, as it is guarded at its entrance by a valve. The blood seems to be delivered by the anterior artery on to the nerve-mass, and, after percolating the muscles and viscera, to divide into two streams—the one returning to the heart by the thoracic ostia, the other passing through the diaphragm and bathing the abdominal organs, finally to reach the heart either by the abdominal ostia or by the posterior vein.
Fig. [218].—Nervous system of Galeodes. abd.g, Abdominal ganglion; ch, cheliceral nerve; ch.f, chitinous fold; ch.r, chitinous rod; g.n, generative nerve; l, labial nerve; st, position of stigma. (After Bernard.)
The nervous system, notwithstanding the fact that the three last thoracic segments are free, is chiefly concentrated into a mass surrounding the oesophagus. Nerves are given off in front to the eyes, the labrum, and the chelicerae, while double nerves radiate to the pedipalps and to the legs. From behind the nerve-mass three nerves emerge, and pass through the diaphragm to enter the abdomen. The median nerve swells into an “abdominal ganglion” just behind the diaphragm, and is then distributed to the diverticula of the alimentary canal. The lateral nerves innervate the generative organs.
The respiratory system consists of a connected network of tracheae communicating with the exterior by the stigmata, whose position has already been described. There are two main lateral trunks extending nearly the whole length of the body, and giving off numerous ramifications, the most important of which are in the cephalothorax, and supply the muscles of the chelicerae and of the other appendages.
The generative glands do not essentially differ from the usual Arachnid type, though the paired ovaries do not fuse to form a ring. There are no external organs, and the sexes can only be distinguished by secondary characteristics, such as the “flagellum” already mentioned.
Classification.—There are about a hundred and seventy species of Solifugae inhabiting the warm regions of the earth. No member of the group is found in England, or in any except the most southern portions of Europe.
Kraepelin[[332]] has divided the group into three families—Galeodidae, Solpugidae, and Hexisopodidae.
Fam. 1. Galeodidae.—The Galeodidae have a lancet-shaped flagellum, directed backwards. There is a characteristic five-toothed plate or comb covering the abdominal stigmata. The tarsus of the fourth leg is three-jointed, and the terminal claws are hairy.