Limbs and Mouth-parts of Crustaceans and Insects. 427 
fourth plus the fifth in the case of the previous division ; no 
marsupium ; motile larvee, which in the case of the lower for ms 
have a Nauplius stage eral large serves of ecdyses ; a short 
heart ; no processes Jor the orifices of the vasa deprentio . > and, 
lastly, by the possession of spermatophores. The third group 
is constituted by the Stomatopoda, which agree in some ot 
their characters with the first and in others with the second 
division, but in various other respects occupy a very isolated 
position. 
III. INSECTA. 
a. Macuinis (§§ 28-35). 
The mandibles of Machilis are homologous with those 
of the Malacostraca; tn form they resemble those of the 
Cumacea, having a well-developed almost cylindrical pars 
molaris, though they are without a lacinia mobilis; cn articu- 
lation and musculature they exhibit a surprising agreement 
with, e. g., Diastylis and Nebalia (vide also § 37), and herein 
diverge to the utmost extent from, e. g., Orthoptera and Coleo- 
pera. 
29. The maxilla are composed of three segments and an 
eight-jointed palpus. The basal segment (cardo) has no 
masticating-lobe ; the second segment is produced into a long 
lobe, which is transversely segmented at the tip; the third 
segment is also produced into a lobe (ga/ea) and the palpus 
arises from its outer side. The structure of the maxille (which 
may be very easily examined in a preparation which has been 
cleared with potash), as regards the origin of the lobes from 
the second and third segments, consequently agrees precisely 
with that of the maxille of the Humatacostraca, while, on the 
other hand, tt vs totally different from that of the maaillule. 
30. In the Isopoda (see a figure in ‘ Cirolanide’’) and 
Amphipoda we find that the maxillipedes are situated very 
close together in the median line, and, moreover, in the latter 
order their first (or first and second) joints become fused 
together; the maxille are articulated in front and at some 
little distance from the median line, while the maxillule are 
attached somewhat further still from the median line, and the 
hypopharynx projects between and before their points of 
articulation ; lastly, the mandibles are inserted far away from 
the median line, obliquely outside and above the maxillule 
and maxille. We meet with a similar arrangement of the 
mandibles, maxille, and labium in Machilis and, e. g., also 
in the Orthoptera and Coleoptera. 
31. L regard the maxille in Machilis (vide §§ 29, 32, and 
BY) as Die -dly homologous with the maxilla (eeennts patr of 
