143 BULLETIN: MUSEUM OF COMPAKATIVE ZOOLOGY. 



cean hypopharynx, and possibly also to the median component of the 

 Diplopod gnathochilariura. 



The first raaxillse in CoUembola and Thysanura develop essentially 

 as in Orthoptera and may be homologized part for part with the maxillae 

 of generalized Pterygota. In Anurida a palpus appears in the embryo, 

 but is resorbed before hatching, indicating the derivation of this genus 

 from a form in which the first maxillary palpi wei'e functional, as they 

 are at present in Orchesella, Tomocerus, and other Collembolan genera. 

 The first maxillae of Campodea are clearly to be homologized with the 

 first of Scolopendrella, the second of Chilopoda, and less clearly with tlie 

 lateral portions of the Diplopod gnathochilarium. The first maxillte of 

 insects pass thi'ough a biraraous condition, as in Crustacea, and the 

 sclerites of these organs appear to be homologous in the two groups ; 

 the first maxillae of Hexapoda, howevei", are equivalent to the second 

 maxillae of Malacostraca. 



The labium in Anurida develops from a pair of papillae, from which 

 the entire gular i-egion is derived. A palpus appears, but is soon re- 

 sorbed, and no galeal and lacinial lobes are differentiated. Upon the 

 whole, the labium among Apterygota is homologous with the same 

 structure of Pterygota, although fewer sclerites are formed in the 

 former group. The labium in insects, homodynamous with the man- 

 dibles and first maxillae, agrees in detail with the first maxillipedes of 

 decapod Crustacea. The labium of Campodea is homologous with the 

 " second maxillae " of Scolopendrella and the maxillipeds of Chilopoda, 

 and is represented in the gnathochilarium of Diplopoda. 



The sides of the face in Anurida develop from two lateral evaginations 

 of the germ band near the mandibular segment, which eventually involve 

 the labral and labial fundaments and complete the buccal cone. The 

 mouth-folds of CoUembola, Campodea, and Japyx are strictly homologous 

 with the genae of Pterygota. The dorsal region of the skull in Anurida 

 does not differentiate into sclerites which may be compared with those 

 of Pterygote insects. 



The tentoruim is inferred to develop from cells which have been pro- 

 liferated from the ectoderm. 



The evidence convinces me that there are just seven somites in the 

 head of Anurida, and that probably the same is true for all Hexapoda. 

 The cephalic somites are successively : ocular, antennal, intercalary, 

 mandibular, superlingual, maxillar}', and labial. As I have found 

 embryonic ganglia for the intercalary and superlingual segments, there 

 are seven cephalic ganglia, one for each somite. Moreover, excepting 



