40 
legs is situated at or behind the middle of the trunk, and if seen from below, near or on 
the lateral margin; as a rule it is shorter than the first pair, the peduncle is not much 
thicker than the rather short inner branch, whereas the outer branch — if there is one — 
is triangular and often ends in a short seta. The terminal sete of the inner branch vary 
as much in length as those of the outer branches of the first pair of legs, and one of them 
can attain to half the length of the animal. The candal stylets are usually situated rather 
close to each other, most frequently near the posterior end of the body, sometimes very much 
to the front about at the middle of the trunk, especially where it is very large, as in Spher. 
Bonnieri and in S. frontalis (pl. VII); in the latter species they even appear in front of the 
second pair of legs. Both stylets as a rule are rather short, sometimes very short, nearly 
cylindrical; one terminal seta on each stylet is often rather or very long, occasionally excee- 
ding in length the above-mentioned long sete on the trunk-legs. — Several species of 
Spheronella deviate now im one, now in more respects, from this description which is based 
on the main bulk of the species. In Spher. modesta (pl. IX, fig. 2f and fig. 2h) the first, 
and especially the second pair of legs are considerably reduced in size etc., whereas the 
caudal stylets are comparatively large and constructed like those of the female (see above). 
In S. decorata (pl. VII, fig. 3f and fig. 3g) the two pairs of trunk-legs are very much 
alike, each leg consisting of a short basal part with two short branches, and each branch 
ending in a thick, but rather short seta; caudal stylets are wanting. Concerning S. microce- 
phala (pl. VILL, fig. 2g and 2h) which deviates considerably and is difficult to understand, 
I refer to my description in the systematic part of this work. In S. curtipes (pl. X, fig. 2f 
and fig. 2@) both pairs of legs are very small, slender and 2-jointed, the caudal stylets are 
quite minute and situated far from each other on the posterior margin of a long and broad, 
but not niuch projecting eminence, the posterior angles of which are decorated with peculiar 
rounded processes and knots (might the whole formation possibly be a reduced abdomen ?). 
It has been mentioned already that trunk-legs and caudal stylets have disappeared altogether 
in several species of Spheronella as well as in Mysidion and Aspidoecia. 
In the species belonging to Stenothocheres and Aspidoecia the body of the male is 
quite naked, whereas all the other species are more or less clothed with hairs. In not 
a few species the frontal margin is furnished with very short hairs or with fine spiniform 
processes (the species of Spheronelia which live as parasites on Cumacea). In nearly all 
species the margin of the lateral borders of the head are trimmed with a series or a stripe 
of hairs usually of medium length, which as a rule extends towards the front in a curve 
round the base of the antennule, ending just in front of it; posteriorly it follows the lateral 
margin up to its curved extremity, whence (or a little in front of it) the stripe continues 
across the sides and the back, now straight on, now curving or in a broken line, now advan- 
cing, now receding obliquely. This line I consider as forming the boundary between the 
head and the trunk, its hairs being now very long (pl. III, fig. 31; pl. VI, fig. 1d), now of 
the same length as those which cover the sides of the trunk. Sometimes (e. g. pl. IV, fig. 3 h) 
