FOLSOM : MOUTir-PARTS OF ANURIDA MARITIMA. 101 



den Embrjonen von Geophilus ziemlich weit hinter dem Munde und 

 diclit vor deu Anlagen der Maudibehi zwei ansehnliche Hocker be- 

 schrieben und abgebildet, welche wahrscheiulich den Hockern auf dem 

 Intercalarsegmente von Campodea homolog sind. Sie werden nacli dem 

 erwahnten Autor immer kleiner und kleiner und sollen endlich ganz 

 verschwinden." 



In Anurida the intercalary thickenings become involved in the folds 

 which form the sides of the face, as I shall describe, but I believe they 

 are not, as Miss Claypole held, the fundaments of those folds. 



In Tomocerus and Orchesella (Folsom, '99, p. li, Plate 2, Figure 9) 

 I have found that " at either end of the [labral] hinge . . . the cuticula 

 is swollen into a conspicuous chitiuous lobe, which projects into the 

 pharynx to fit against a corresponding prominence of the mandible," etc. 

 As these lobes in the adult occupy precisely the same positions as those 

 of Campodea (Uzel, '98, Taf. VI,, Figur 85, ifit.), I believe them to be 

 intercalary appendages. In Anurida no such lobes exist. 



In Chilopods, two pairs of antennal fundaments appear (Heymons, 'g?*", 

 p. 4, Figur 1, Scolopendra), and the second, which alone become func- 

 tional, are equivalent in position to the intercalary appendages of 

 Apterygota as well as the antennae of Diplopods (cf. Heymons, 97'', p. 7, 

 Figur 2, Glomeris). 



The equivalence of the tritocerebrum in Hexapoda and Crustacea was 

 first shown in detail by Viallanes. His account ('87, pp. 105-108) is 

 too long to be quoted in full, but he concludes : " Les deux lobes con- 

 stitutifs du tritocerebron de I'lnsecte, et que j'ai designes sous le nom 

 de lobes tritocerebraux, representent exactement les deux ganglions 

 CBSophagiens du Crustace ; ils donnent naissance aux memes racines 

 nerveuses, ils sont, comme ces derniers, unis au-dessous de I'cEsophage 

 par la commissure transverse de I'anneau oesophagien." 



Many authors (Korschelt und Heider, '90-93, p. 906) agree in homolo- 

 gizing the antennae of Hexapoda, innervated from the deutocerebriim, 

 with the first antennae of Crustacea ; also in homologizing the mandibles 

 of both gi'oups. Therefore only the intervening appendages of the trito- 

 cerebrum remain to represent the second antennae of Crustacea. 



An intercalary segment, then, is to be recognized among Pterygota, 

 at least in the more generalized forms, and especially among the primi- 

 tive Apterygota, and in the latter group it may bear rudimentary appen- 

 dages, even in the adult. The intercalary segment is to '^e regarded as 

 equivalent in morphological value to any primary head-segment, — es- 

 pecially because it bears a primitive ganglion, — and it constitutes the 



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