folsom: mouth-pakts 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 Campodeidse. Although Packard ('98, p. 15) 

 states, " In the Chilopoda also the parts of the head, except the epi- 

 craniuni, 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 Ephemeridoe, a " lacinia 

 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 Musculatnr 

 8tiramen sie erstaunend uberein mit z. B. Dkistylis und Nehalia.^' de- 

 ferring to Campodea, Japyx, and Collembola, he remarks (pp. 208-209), 

 "Die Musculatur der Mandibeln ist noch mehr der Crustaceen ahnlich 

 als der Musculatur der Machilis. Vergleiche Meinert's Figur von 

 Jaj'iyx m\t inemev Figur von Diastylis Goodsiri in ' Dijmphna-Togtet ' 

 (ich habe nur die drei grossten Muskeln oder ihre Sehnen wiedergege- 

 ben) oder mit Sars ' Figur von Diastylis sculpta, und man wird betroffen 

 von der erstaunlicheu 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, 

 tl)G most primitive form. The mandibles and maxillce are homodyna- 

 mous, and the former are homologous with the mandibles of Scolopen- 

 drella, Crustacea, and prol)ably Diplopoda. 



