While the mandibles are generally regarded as composed of a single piece, in Campodea and Machilis there appears to be an additional basal piece apparently corresponding to the stipes of the first maxilla, and separated by a faint suture from the molar or distal joint. In Campodea there is a minute movable appendage figured both by Meinert and by Nassonow, which appears to represent the lacinia of the maxilla (Fig. 48). Wood-Mason has observed in the mandibles of the embryo of a Javanese cockroach, _Blatta (Panesthia) javanica_, indications of “the same number of joints as in that of chilognathous myriopods, or one less than in that of Machilis.” Also he adds: “In both ‘larvæ’ and adults of _Panesthia javanica_ a faint groove crosses the ‘back’ of the mandible at the base. This groove appears to be the remains of the joint between the third and apical segments of the formerly 4–segmented mandibles.” [Illustration: FIG. 46.—Various forms of mandibles. _A_, right and left of Termopsis. _A′_, showing at the shaded portion the “molar” of Smith. _B_, _Termes flavipes_, soldier; _md_, its mandible. _C_, Panorpa. ] [Illustration: FIG. 47.—_Chiasognathus grantii_, reduced. Male.—After Darwin. ] [Illustration: FIG. 48.—Mandible of Campodea: _l_, prostheca or lacinia; _g_, galea; _f_, _f_, flexor muscles; _e_, extensor; _r_, _r_, retractor; _rt_, muscle retaining the mandible in its place.—After Meinert. _A_, extremity of the same.—After Nassonow. ] [Illustration: FIG. 49.—Mandible of _Passalus cornutus_ with the prostheca (_l_): _A_, that of a Nicaraguan species; _a_, inside, _b_, outside view, with the muscle. ] He also refers to the _prostheca_ of Kirby and Spence (Fig. 49), which he thinks appears to be a mandibular lacinia homologous with it in Staphylinidæ and other beetles (J. B. Smith also considers it as “homologous to the lacinia of the maxilla”), and on examining it in _P. cornutus_ and a Nicaragua species (Fig. 49), we adopt his view, since we have found that it is freely movable and attached by a tendon and muscle to the galea. In the rove beetles (Goërius, Staphylinus, etc.) and in the subaquatic Heteroceridæ, instead of a molar process, is a membranous setose appendage not unlike the coxal appendages of Scolopendrella, movably articulated to the jaw, which he thinks answers to the molar branch of the jaws in Blatta and Machilis. “It has its homologue in the diminutive Trichopterygidæ in the firmly chitinized quadrant-shaped second mandibular joint, which is used in a peculiar manner in crushing the food”; also in the movable tooth of the Passalidæ, and in the membranous inner lobe of the mandibles of the goliath-beetles, etc.