FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 101 
den Embryonen von Geophilus ziemlich weit hinter dem Munde und 
dicht vor den Anlagen der Mandibelnu zwei ansehnliche Hocker be- 
schrieben und abgebildet, welche wahrscheinlich den Héckern auf dem 
Intercalarsegmente von Campodea homolog sind. Sie werden nach dem 
erwihnten 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. 14, Plate 2, Figure 9) 
I have found that “at either end of the [labral] hinge... the cuticula 
is swollen into a conspicuous chitinous lobe, which projects into the 
pharynx to fit against a corresponding prominence of the mandible,” ete. 
As these lobes in the adult occupy precisely the same positions as those 
of Campodea (Uzel, ’98, Taf. VI., Figur 85, int.), I believe them to be 
intercalary appendages. In Anurida no such lobes exist. 
In Chilopods, two pairs of antennal fundaments appear (Heymons, '97°, 
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 antenne 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 tritocérébron de l’Insecte, et que j’ai désignés sous le nom 
de lobes tritocérébraux, représentent exactement les deux ganglions 
cesophagiens du Crustacé; ils donnent naissance aux mémes racines 
nerveuses, ils sont, comme ces derniers, unis au-dessous de lcesophage 
par la commissure transverse de l’anneau cesophagien.” 
Many authors (Korschelt und Heider, ’90-93, p. 906) agree in homolo- 
gizing the antennz of Hexapoda, innervated from the deutocerebrum, 
with the first antennz of Crustacea ; also in homologizing the mandibles 
of both groups. Therefore only the intervening appendages of the trito- 
cerebrum remain to represent the second antenne 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 be 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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