20 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



in the chitinized apex. Each nerve fibre, soon after penetrating the 

 mandible, becomes enlarged to contain a small round nucleus (Figs. 16 

 and 17, cl.gn.). The mandible is lined with a thick layer of deeply 

 pigmented hypodermis (tidrm.), the confluent cells of which contain 

 large oval nuclei (shown in cross section in Fig. 16), strongly contrast- 

 ing in size with the nerve nuclei of the core of the mandible. 



Maxilla. 



The maxilla? (Plate 3, Fig. 18) are about as long as the mandibles, 

 and composed of two specialized regions : first, an anterior terminal 

 movable lobe (Fig. 18, cpt.), which is subdivided into several smaller 

 lobes and teeth ; secondly, a posterior framework bearing muscles and 

 supporting the terminal lobe and the palpus. The dorsal and outer 

 portion of the terminal lobe is wholly chitinous and bears three stout, 

 incurving claws (Fig. 19, get.). This portion de Olfers ('62) compares 

 with the galea of Orthoptera, and Packard ('71, p. 100), referring to 

 the mouth-parts of Tomocerus plumbeus, writes, "The middle lobe, or 

 galea, is nearly obsolete, though I think I have seen it in Smynthurus, 

 where it forms a lobe on the outside of the lacinia." Von Stummer- 

 Traunfels ('91, pp. 221, 223), however, says, " Es ist mir darum sehr 

 zweifelhaft, ob dieser Theil des Kieferapparates die Deutung als aussere 

 Lade wirklich verdient. . . . Bei Japyx noch zweifach gegliedert, ist 

 er bei Campodea schon mehr reduch't und fehlt bei den Collembolen 

 ganzlich." The careful comparative studies of the last mentioned author 

 give much weight to his opinion. Underlying the tridentate lobe, or 

 so called galea, are four chitinous lobes, or lamellae, each of which bears 

 on its inner margin a comb of fine teeth. Three of these lobes are 

 falcate in form, and the fourth or inmost lobe (Fig. 19, Icn.) bears a 

 prominent hook on its upper surface. These four fringed lobes probably 

 represent the lacinia, or inner lobe, of other insects. The seven lobes 

 and claws described appear to be firmly united basally, and, if so, cannot 

 move separately, but must all move together by means of the articula- 

 tion (Fig. 19, ate.) at the apex of the stipes. The movement is lateral 

 only, and the adduction is accomplished by muscles which terminate in 

 a slender chitinous rod (Figs. 18, 19, and 20, bac.) having the function 

 of a tendon, and so named by von Stummer-Trauufels. T^iis tendon is 

 attached to the base of the inmost lobe of the lacinia. 



Considering now the framework of the maxilla, the stipes (Figs. 18- 

 20, stp.) is a stout chitinous structure, the form of which I may roughly 



