126 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
formulated a significant law — “dass man drei Glieder im Stamm von 
allen gespalteten Gliedmassen bei den Crustaceen als ein primares 
Verhiltniss annehmen muss, und diese Zahl hat sich, wenigstens in 
den angefiithrten Fiillen, deutlich erhalten.” In fact, Hansen himself 
(p. 206) has homologized the first maxillz of Machilis with the second 
maxilla of Crustacea, on account of the three axial segments and the 
position of the palpus, saying: “Der Bau der Maxillen . . . stimmt 
also genau mit den Maxillen der Eumalacostraken.” 
The axial segments of the Crustacean appendage are on this view 
successively equivalent to cardo, stipes, and palpifer of Hexapoda. 
It must be admitted that these anatomical agreements, if appealed to 
alone, may logically be used to support other views than my own, since 
all the Crustacean appendages are constructed upon the same plan; but 
the equivalence of the neuromeres in Hexapoda and Crustacea is a mat- 
ter of the greatest significance. Viallanes has proved that the first three 
neuromeres in the two groups agree in great detail, and I find that his con- 
clusions apply equally well to the succeeding neuromeres, It is very sig- 
nificant that in most cases the appendages of equivalent somites have 
the same function in the two groups, and that all the paired nerves of 
the head in Collembola agree exactly in position with those of decapod 
Crustacea. 
Summarizing: The first maxille of Apterygota develop in all essential 
respects like those of Orthoptera, with which they may be homologized 
in detail. In Anurida a palpus appears, but is resorbed before hatching, 
indicating the descent of Anurida from a form in which the first maxil- 
lary palpi were functional. The first maxillee of Campodea are clearly 
to be homologized with those of Scolopendrella, and less clearly with 
the lateral portions of the Diplopod gnathochilarium. The first maxillee 
of Hexapoda pass through a biramous stage, such as obtains among 
Crustacea, are comparable with Crustacean second maxille in some 
detail, and are homologous with those of Malacostraca. 
Labium. 
The fundaments of the labium, or “second maxille,”’ appear next 
after those of the first maxille, and at Stage 1 (Plate 1, Figure 1; 
Plate 2, Figure 8, mx.) are a pair of simple conical elevations rising 
perpendicularly from the germ band and slightly longer than the funda- 
ments of the mandibles and first maxille. In the following stage (2) 
they are longer and more cylindrical (Figure 2); in Stage 3 (Figure 3) 
