424 Dr. H. J. Hansen on the Morphology of the 
Nushaum), which must undoubtedly be homologous with the 
furcain Nebalia; they are relatively of large size, especially 
in the penultimate larval stage, and are probably cast off in 
the penultimate ecdysis in the marsupium. 
19, The Cumacea, Tanaide (which must be elevated into 
a separate order), Isopoda, and Amphipoda agree exactly in 
the structure of the mouth-parts (not including the suppression 
of the exopodite of the maxille, the suppression of the 
Jacinia mobilis in isolated parasitic forms, and_ similar 
secondary reductions) and thoracic appendages with the 
Mysidee in all the characters which are mentioned in § 18. 
It is very easy to study the structure of the maxille and 
maxillule in Amphipoda (véde “ Dijmphna-Togtet ”) and 
Isopoda (vide “ Cirolanide!”’). In certain Isopods the stem of 
the antenne is distinctly three-jointed, but in the majority of 
forms the first segment disappears and probably fuses with 
the head. Kven where the so-called epimeres are strongly 
developed (as in certain Amphipods) the coxopodite (or the 
interval between the body and the articulation of the second 
segment) is always short and several times shorter than the 
basipodite. 
20. In many Isopods the first segment of the six hindmost 
pairs of thoracic limbs is small and movable; in many other 
genera it develops as an “ epimere,” which, e. g. in Idothea 
entomon, is very large, marked off on the dorsal side by an 
arthrodial furrow, and on the ventral surface fused with the 
ventral ridge (‘‘ Bauchschiene”’) ; but in Jdothea hectica the 
upper arthrodial furrow has also disappeared and the ‘ epi- 
mere ”’ has certainly not been reduced to the point of disap- 
pearance, but has become fused with the segments of the 
body and forms larger or smaller portions of their sides 
(cf. §§ 24 and 49). 
21. In certain Isopods (Janira) we find a large thorn upon 
the seventh segment of the thoracic appendages, articulated 
beneath the cheliform eighth segment, so that the foot is 
said to have two claws (cf. § 51). 
22. ‘The Euphausiide are a long way removed from the 
Myside in consequence of a series of characters, certain of 
which only will be mentioned here. The stem of the antenne 
is two-jointed ; the mandibles have no lacinia mobilis. The 
limbs are compored of only seven segments (they are without 
the “claw”’). The “knee” lies between the fourth and fitth 
segments ; the first segment is almost equally as large as 
the second. J suppose the segments beyond the knee to be 
homologous with the sixth, seventh, and eighth (claw) 
segments in Mysis, and the fourth segment to be homologous 
