120 bulletin: museum of comparative zoology. 



cause the paired mouth-parts are still at right angles to the germ band 

 long after involution has occurred (Stage 5, Figures 5, 20). During 

 this stage (7) the first maxill<e are attenuated toward their free ends ; 

 a ventral view (Plate 5, Figure 29, mx.^) shows their position in rela- 

 tion to the lingua, and the extent of their convergence toward each other. 

 The maxilla is quite unattached to the pharyngeal pocket (Plate 7, Fig- 

 ures 44-50, cav. hue.) in which it lies, except where the margin of its 

 basal aperture becomes confluent with the wall of the pocket (Figure 50) ; 

 it has the form of a modified cone with an oblique, dorso-mesal, basal 

 opening, as shown in transections (Figures 44-50, mx}). The parts 

 named stipes and chitinous rod in my paper upon Orchesella are, as I 

 have since found in that genus and in Anurida, distinguished simply by 

 a greater deposition of chitin, and are connected above and below by 

 delicate chitinized membranes, which I did not recognize until influ- 

 enced by embryology to search for them. The "chitinous rod," then, is 

 proved both by anatomy and development to be but a part of the 

 stipes. 



During this stage (7) certain important differentiations of the first 

 maxillse are observable, if those organs are dissected out. The articula- 

 tion between stipes and cardo (Plate 6, Figure 38, ate.) appears super- 

 ficially as a notch, and in frontal section as a' less chitinized region, 

 as might be expected ; in a small hypodermal pocket is formed the stipal 

 projection (Figure 38, ^^?>) noticeable in the finished organ. The cardo, 

 now transverse in position, was formerly the basal region of the lateral 

 surface of the primary maxillary fundament, before the basal attachment 

 became oblique. The articulation between the cardo and lingual stalk 

 was described on page 112. 



In tliis stage, too, the head of the maxilla becomes vaguely separated 

 from the stipes by a constriction (Plate 5, Figure 29). Later, the con- 

 striction is more pronounced (Plate 4, Figure 25), and the apex of the 

 head is fashioned into an acute curving lobe, — the fundament of the 

 galea (Plate 4, Figure 26, ga.) or " aussere Lade." The " head " is lined 

 with a continuous layer of hypodermis cells. Next, on the mesal side 

 of the head, a second lobe appears, the lacinia (Jen.), or " innerc Lade." 

 Both galea and lacinia, then, become toothed on the mesal face, the 

 teeth of the latter being produced each by a single cell ; the larger tcctli 

 of the former are secreted each hy many cells. Eventually (Plate 6, 

 Figure 39) the galea {gn.) becomes thickly chitinized except for a 

 <;entral hollow core, but the lacinia Qcn.) remains thinly cliitini/ed even 

 in the adult. As in the mandibles, the hypodermis is finally excluded 



