50 
the female and the male, for not only are the antenne situated a little outside its base, but 
the maxillule are found quite, or nearly quite, outside it. The general structure of the 
mouth is like that of the adult animal; the mandibles are frequently seen in the opening, 
but the hairs of the mouth-border are always short, frequently so short. that they can only 
be discovered with the greatest difficulty. 
The Maxillule are difficult to understand, and it is very difficult to discover all 
their sete. As mentioned above, in the various illustrations of the larve I have drawn 
what I have found, but I am pretty sure that I have not everywhere found all the elements. 
The highest development I met in Spher. Calliopii (pl. ILI, fig. 31) as well as in the species 
which are parasitic in the marsupium of Cumacea, as Spher. decorata (pl. VIL, fig. 31), 
S. modesta (pl. LX, fig. 2i) and S. dispar (pl. LX, fig. 3k). In these figures we see obliquely 
behind and outside the rostrum on each side four sete, the two hindmost of which are 
coalescent or adjacent at their base, one or both of them being plumose.  Obliquely from 
these and somewhat nearer to the rostrum proceeds a third seta, which turns. straight 
towards the front, and obliquely before this one again, there is a fourth, shorter seta. I[ 
suppose that all these four setz belong to one maxillula, the basal part of which is not 
separated from the ventral side of the head. In Spher. marginata (pl. XIII, fig. 6g) the 
innermost seta is reduced to a short process. In most of the other forms I have only been 
able to find three sete, e.g. in Spher. microcephala (pl. VIL, fig. 2i) and in Choniostoma 
mirabile (pl. XT, fig. le), or two, or only one. In Stenothocheres egregius (pl. I, fig. 11) I have 
found a maxillula (e) which reminds me much of those in the adult animals, as it consists 
of a short, basal part, from which proceed two thick sete, of which the hindmost is shorter, 
the foremost very long. In the genus Homoeoscelis (pl. I, fig. 11 and pl. XIII, fig. 1h) I 
have been unable to find vestiges of maxillule. 
The Maxille nearly always consist of three distinct joints, and are very much like 
those of the adult animals, though the stout basal joint, as a rule, is narrower and the two 
next joints are longer than in the adult; these two joints are slender, and the last one 
somewhat curved and claw-like. In Homoeoscelis only the two last joimts are entirely 
coalescent, forming one curved joint, which moreover along the larger part of both margins 
is provided with exceedingly fine and short setiform processes (pl. XIII, fig. 1h). As a rule 
all three joints are simple and smooth, but in those species of Spheronella which live in 
the marsupium of Cumacea, the inner margin of the third jomt is coarsely or finely serrated, 
and the first joint has on its inner margin, against which the second joint can be folded 
up, a double row of fine cylindrical processes (pl. VIII, fig. 8n and fig. 30), and a similar 
decoration is seen in Spher. Maunnopsidis (pl. X, fig. 4d). — The two maxille are always 
situated at some — usually at a considerable — distance from each other. 
The Maaillipeds, as a rule, are placed close behind the maxille, and also generally 
somewhat closer to the median line than these; in Homoeoscelis only (pl. Il, fig. 11 and 
pl. XII, fig. 1h) there is a great distance between these two pairs of appendages. The 
