106 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
development of the mandibles, as shown by Heymons (’97°%, Taf. XXX., 
Figuren 13; 15, 17, 20), is simple, and agrees with that of Anurida and 
Campodea. The finished mandible of Machilis (Oudemauns, ’88, Plate 
IL., Figuren 25, 26), especially, recalls that of Campodea and Collem- 
bola by its elongated hollow fulcrum, oblique aperture, basal pivot, 
distinct head, and (as in Orchesella) well-developed molar surface ; 
moreover, the adductors originate ona tentorium and are inserted within 
the mandibles (Oudemans, ’88, Taf. 1, Figur 19; Wood-Mason, 779, 
p- 148, Figure 1). Wood-Mason named the apex of the mandible “ ex- 
opodite” and the molar lobe “ endopodite,” but upon superficial grounds, 
if one may judge from the evidence of embryology. Both lobes may 
together represent the endopodite ; but the exopodite, or palpus,.is un- 
represented in the mandible, and it is a secondary lobe of the primary, 
or stipal, fundament, in the first and second maxilla. Wood-Mason 
(79) pointed out many interesting similarities which Machilis and 
Lepisma bear to the most generalized Orthopteran family, the Blattide, 
and remarked (p. 149), concerning the pivot of Machilis, that “the pos- 
terior ball-shaped condyle of mandibulated insects, clearly foreshadowed 
in the myriapod, is here fully formed and provided with a distinet neck.” 
The mandibles of Lepisma, however, more closely approach the Or- 
thopteran type in being compact (v. Stummer-Traunfels, 91, Taf. IT., 
Figuren 5, 6) and partly solidified, and in having broad incisive teeth, 
a molar surface like that of Orthoptera, and broadly attached adductors. 
The muscles are said by Oudemans (’88, p. 187) to resemble those of 
Machilis. V. Stummer-Traunfels represents the adductors only, and it 
may well be that the muscles are really much fewer than in Campodea | 
and Collembola, such a reduction in number, if it occurs, being an 
approach to the Orthopteran type, in which but two mandibular muscles 
exist — a stout adductor and a slender abductor. 
As to the development of the mandibles in Orthoptera, very little has 
been published. Ayers (’84, p. 241, Plate 18, Figures 20-22) says that 
in @icanthus “the three oral appendages are trilobed ; the lobation is 
most prominent in the second maxillary and least in the mandibular 
appendage. The primitive appendage is first divided into two lobes, 
and the inner of these becomes secondarily divided into two.’ The 
three lobes doubtless represent palpus, galea, and lacinia. Korotneff 
(85, Taf. XXIX., Figure 6) figures lobed mandibular fundaments for 
aryllotalpa, In other Orthoptera such lobation has not been recorded. 
In Blatta, according to Wheeler (’89, p. 348), “There are apparently 
no traces of lobation in the mandibles.” Packard (’83*, p. 279) says, 
