96 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Taf. II., Figuren 19, 29), and examples might be multiplied to show 
that the labrum does not represent a pair of appendages. The view 
held by Kowalevsky, Carriere and others, that it did, was based chiefly 
upon anatomical evidence, which has since been disproved by Heymons 
(95) and others. (See Packard, ’98, pp. 42-43.) 
Scolopendrella (Latzel, 84, p. 8, Taf. I., Figur 4; Grassi, ’86%, p. 15, 
Tav. IL., Figura 6) has a simple, emarginate, six-toothed labrum, and, 
like Hexapoda, a distinct, subtriangular clypeus. Moreoyer, as Packard 
(98, p. 22) has affirmed, it has a V-shaped tergal suture, which exists 
also in the more generalized insects, but is absent in Myriopods. 
In Diplopoda, an upper lip is present as a transverse plate, fused, 
however, with the cranium. 
In Chilopoda, a similar labrum is present, but is not always basally 
fused, and frequently consists of three transversely placed sclerites. It 
originates as a simple median lobe (Heymons, ’97°, p. 4, Figur 1, Scolo- 
pendra). 
In Crustacea the upper lip is derived from a median, unpaired evagi- 
nation corresponding almost exactly in position with the labral funda- 
ment among insects. 
Among insects, then, the labrum and clypeus develop from a median 
evagination between the procephalic lobes, and give no satisfactory evi- 
dence of paired origin. The same statement applies also to Crustacea, 
and, as far as is known, to Myriopods. 
Antenne. 
The antenne are the first paired organs to appear. They develop 
from the posterior boundaries of the procephalic lobes, and at Stage 1 
(Plate 1, Figure 1, Plate 2, Figure 8, at.) are stout cylindrical papille 
already faintly constricted into two segments. As Figure 8 shows, they 
are more lateral than the other paired fundaments, and at first far be- 
hind the labrum. Sections prove them to be simple ectodermal evagina- 
tions, like all the other appendieular fundaments. 
At Stages 2 and 3 (Plate 1, Figures 2, 3, at.) the antenne are longer 
and usually composed of three segments. In Figure 2 the fourth seg- 
ment, which normally appears later than Stage 2, is suggested. They 
have now moved forward to positions near the labrum; in Stage 4 
(Plate 1, Figure 4; Plate 3, Figure 12, at.) they lie on the two sides 
of that appendage, and in Stage 5 (Plate 1, Figure 5; Plate 3, Figure 
21, at.) they have attained a position farther forward than the upper lip. 
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