FOLSOM: MOUTH-PARTS OF AXURIDA MARITIMA. 147 



The antenuEe of Apterygota evaginate from the posterior boundaries 

 of the procephaUc lobes, and therefore agree with those of Pterygota in 

 this respect. In both groups the antennae are at first post-oral and sub- 

 sequently pre-oral in position. 



The deutocerebrum of insects is homologous with that of Crustacea, 

 and the antennae of Hexapoda are equivalent to the antennules of 

 Crustacea and the embryonic prseantennse of Chilopoda. 



Premandibular, or intercalary, appendages exist in the embryo of 

 Anurida, and appear to be represented even in the adults of several 

 Apterygote genera. The tritocerebrum of Apterygota is homologous 

 with that of Orthoptera and decapod Crustacea, and the rudimentary 

 premandibular appendages of CoUembola and Thysanura represent the 

 second anteunee of decapod Crustacea and probably the antennae of 

 Diplopoda and Chilopoda. A distinct primitive ganglion occurs in the 

 intercalary segment of Anurida, therefore the segment must be regai'ded 

 as one of the primary head-segments. 



The mandibles of Apterygota develop from a pair of simple papillae, 

 the bases of which become oblique. Xo trace of lobation occurs except 

 in Campodea. The mandibles of CoUembola and Thysanura are homo- 

 dynamous with the maxillae and homologous with the mandibles of 

 Pterygota, Scolopendrella, Crustacea, and probably Diplopoda and 

 Chilopoda. 



The " hypopharynx " in Apterygota is a compound structure consist- 

 ing of two dorsal " superlinguae," — as I have called them, — which 

 develop from a pair of papillae between the mandibular and first maxil- 

 lary segments, and also a ventral lingua, which originates independently 

 as a median unpaired evagination on the first maxillary segment. The 

 two chitinous '"'lingual stalks," which are most highly developed among 

 Apterygota, arise in superficial grooves of the ectoderm. The hypo- 

 pharynx of Apterygota is undoubtedly homologous with that of Pterv- 

 gota ; although, in the latter group, the lingua and superlinguas become 

 united together and the lingual stalks become rudimentary. In Anurida 

 a distinct neuromere exists for the " superlinguae ; " therefore it is neces- 

 sary to recognize the superlingual segment as equivalent in morphologi- 

 cal value to the other primary somites. The superlinguae are homologous 

 with the first maxillae of Malacostraca and Chilopoda and are anatomi- 

 cally represented in the labial plate of Diplopoda. In order to avoid 

 confusion, the terms " paraglossae " and "ligula" should not be applied 

 to the constituents of the hypopharynx, but are better restricted to tlie 

 labium of insects. The lingua of Hexapoda is equivalent to the Crusta- 



