Fig. [231].—Mouth-parts of Phalangium. A, B, C, Gnathobases of pedipalp and first and second legs; ch, chelicera; ep, epistome; lab, labium; m, mouth; ped, pedipalp; pre.ep, pre-epistome; st, sternum, shown by the removal of the anterior part of the genital process, which extends to the dotted line; 1, 2, 3, 4, legs.
The anterior wall of the mouth is formed by a beak-like plate, the “epistome,” the basal portion of which is covered externally by a second plate, for which Simon[[340]] proposes the name “pre-epistome.” In some Phalangids there are three little chitinous plates, one median and two lateral, on the clypeus, between the anterior border of the carapace and the insertion of the chelicerae. They are best seen in Nemastoma.
The abdomen always presents evidences of segmentation, though there is a difference of opinion as to the number of segments of which it is composed. This is due to the already mentioned partial or complete fusion of the anterior segments with the cephalothorax. From the admirable researches of Hansen and Sörensen[[341]] it seems likely that the normal number of abdominal segments is ten. Ventrally, the abdomen is produced forward into a “sternal process” which is capped by a genital plate, hardly distinguishable in the Phalangidae, but readily visible in the other families, which surrounds and masks the unpaired genital orifice. Two stigmata or breathing pores are situated on the sides of the first ventral plate, which these authors consider to be composed of two fused sternites.
As in other Arachnids there are six pairs of appendages articulated to the cephalothorax. They are the chelicerae, the pedipalpi, and the four pairs of ambulatory legs.
The chelicerae are three-jointed and chelate, the second joint having its inner portion produced into an apophysis to which the final joint is apposed. In certain forms (Gonyleptidae, Ischyropsalis) the chelicerae are remarkably long, and may considerably exceed the total length of the trunk.
The pedipalpi are six-jointed, possessing coxa, trochanter, femur, patella, tibia, and tarsus. They are leg-like and are never chelate, but in some forms terminate in a single movable claw. The coxal joints are provided with maxillary plates.
The legs are normally seven-jointed, as in Spiders, the penultimate joint being the metatarsus. The tarsus is always multi-articulate, the number of its joints being variable. It bears terminally one or two simple claws. “False articulations” (where the parts are not inserted one into the other, but are only marked off by a membranous ring) are of frequent occurrence in the legs of these creatures. The first legs, like the pedipalps, bear maxillary plates, as do also the second in most Phalangids. The maxillae of the second legs are, however, entirely absent in Nemastoma, and rudimentary in the Gonyleptidae and the Ischyropsalidae. The coxae of the legs are all largely developed, but are not capable of free motion, being soldered to, and practically forming part of, the cephalothoracic floor. In some forms they are only separated from one another by slight grooves. The extreme length of the legs, and their hard and brittle nature, are characteristic features of the Phalangids, though in some species (Trogulidae) they are comparatively short. The first pair of legs are always the shortest, and the second the longest.
The sexual organs of Phalangids are ordinarily concealed, and the sexes can only be distinguished by certain very variable secondary characters, the males being usually smaller of body and longer of leg than the females, besides being more distinctly coloured and being armed with more numerous and longer spines. Sometimes the male chelicerae are highly characteristic.
Phalangids are usually destitute of spinning organs, but such have been discovered, in a rudimentary state, in the Cyphophthalmi, which are said to spin slight webs.