FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 109 
equivalent to those of Chilognatha, and, indeed, to the mandibles of Hexa- 
poda and Crustacea. In the mandibles of Scolopendra (Meinert, ’83, 
Taf. II., Figur 9), for example, there can be recognized cardo and stipes, 
a distinct head with galeal and lacinial lobes, and even muscles exactly 
comparable with the adductors and retractors of the mandible in Campodea 
and Japyx. ‘The affinities of the Chilopods are, however, with the Dip- 
lopods, — from the stem-form of which they may have developed, — 
rather than with the Campodeide. Although Packard (98, p. 15) 
states, “In the Chilopoda also the parts of the head, except the epi- 
cranium, are not homologous with those of insects, neither are the 
mouth-parts,”’ there is really much indirect evidence of homology 
with the mouth-parts of insects through Diplopoda, Symphyla, and 
Thysanura, as is indicated above. 
The mandibles of Crustacea have usually been considered homologous 
with those of insects. In Malacostraca (Reichenbach, ’86), as in in- 
sects, the mandibular fundaments are a pair of appendages of the fourth 
primitive segment. In insects the exopodite (palpus) is absent, but in 
such generalized groups as Campodea and certain Ephemeride, a “ Jacinia 
mobilis” is present ; in Malacostraca the palpus is present, and like- 
wise, according to Hansen, a similar lacinia is found in the groups 
Mysida, Cumacea, Isopoda, and Amphipoda, although not in Decapoda. 
Among insects, the Thysanura most nearly approach Crustacea. 
Hansen (93, pp. 205-206) says of Machilis: ‘Die Mandibeln sind 
homolog mit denen der Malacostraken ; in Form sind sie denen der 
Cumaceen ahnlich, mit einer gut entwickelten, fast cylindrischen Pars 
molaris, doch ohne Lacinia mobilis; in Einlenkung und Musculatur 
stimmen sie erstaunend iiberein mit z. B. Diastylis und Nebalia.” Re- 
ferring to Campodea, Japyx, and Collembola, he remarks (pp. 208-209), 
‘Die Musculatur der Mandibeln ist noch mehr der Crustaceen iihnlich 
als der Musculatur der Machilis. Vergleiche Meinert’s Figur von 
Japyx mit meiner Figur von Diastylis Goodsiri in ‘ Dijmphna-Togtet’ 
(ich habe nur die drei gréssten Muskeln oder ihre Sehnen wiedergege- 
ben) oder mit Sars’ Figur von Diastylis sculpta, und man wird betroffen 
von der erstaunlichen Uebereinstimmung in Form und Richtung der 
Muskeln und der grossen medianen Muskelplatte.”’ 
In conclusion, the mandibles of Apterygota agree in development with 
those of Orthoptera, but show no trace of lobation except in Campodea, 
the most primitive form. The mandibles and maxillze are homodyna- 
mous, and the former are homologous with the mandibles of Scolopen- 
drella, Crustacea, and probably Diplopoda. 
