26 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



more rigid (Fig. 22, cht.). The inner margins of the two appendages 

 approximate each other, leaving an elliptical aperture however (Fig. 

 22, lu.), beneath which may be seen a single median row of fine teeth 

 belonging to the dorsal surface of the glossa (Fig. 22). The inner edge 

 of either paraglossa is furnished with teeth along its posterior half. 

 Considering the teeth successively, the most anterior are blunt and 

 lie in a frontal plane ; as we pass backward the teeth are not only 

 longer and more slender, but, as they approach the median plane, also 

 become gradually erect, so that at length the posterior teeth project in 

 a parasagittal plane. This change in direction is brought about by a 

 curvature of the edge of the paraglossa, the dorsal surface of which, in 

 passing backward, gradually becomes more concave, causing the inner 

 margin to curve upward, or forward, as the parts naturally lie. The 

 concavity of the paraglossa matches the convexity of the molar surface 

 of the mandible on the same side of the head, and the sagittal teeth of 

 the paraglossse normally intervene between the grinding faces of the 

 mandibles (Plate 4, Fig. 30, ?nd.). 



I find no well marked bundle of nerve fibres for the glossa and para- 

 glossa;, but many separate fibres, each from a ganglion cell, are given off 

 directly from the infra-oesophageal ganglion and penetrate between the 

 hypodermal cells of the tongue, which are for the most part attenuated 

 like the filamentous chitin-forming cells of the labrum. 



The glossa (Plate 3, Fig. 23), situated under the paraglossse which it 

 bears, is an elongated, unpaired, chitinous organ, the median furrows of 

 which however probably indicate its derivation from a paired condition. 

 Three regions may be distinguished : a terminal, free portion (Plate 1, 

 Fig. 3, gls.), an intermediate region with which the paraglossa? are 

 fused, and a basal part, consisting of a pair of supporting stalks (pd., 

 Plate 2, Fig. 10, Plate 3, Figs. 22, 23). The free portion is oval in 

 cross section (Plate 4, Fig. 28, gls.) ; viewed from above (Plate 3, Fig. 

 23) it terminates in front in an oval transparent lobe, across the end 

 of which is a subterminal dorsal fold or ridge (Fig. 23, pli.), which 

 interlocks with the labrum (Plate 1, Fig. 3). The upper surface of the 

 terminal lobe is provided on either side with a curving row of minute 

 teeth (Fig. 23, de.) borne upon a thickened chitinous ridge. A median 

 dorsal groove is present, in the course of which occurs what appears to 

 be an opening (Fig. 23, of.) into the interior of the glossa. The inter- 

 mediate region bears the paraglossae, the basal halves of which merge 

 with the glossa to form a single body ; the cavity of either paraglossa 

 also becomes confluent with that of the glossa (Plate 4, Fig. 29). The 



