184 M.W. Lilljeborg on two remarkable Crustacea 
portantes. Apud specimina juniora matricem minimam observa- 
vimus. Ova in matrice semper serie simplici posita fuerunt. 
Oculus magnus, ex magno numero oculorum simplicium compositus, 
partem anteriorem capitis explens, pigmento fusco-nigro. Pone 
oculum videmus ganglia cephalica coalita, alterum pone alterum 
positum, anteriore naturam ganglii ophthalmici preebente. E parte 
posteriore exit nervus, qui postea in duos nervos, qui cesophagum 
ad latera circumdant, divisus est. Interdum hic nervus ab initio 
est divisus. 
Motus saltatorius, non celeritate insignis. Victus ex animalculis 
constat. Pullos Cyclopum prehensos pedibus Leptodore vidi. 
Longitudo corporis cum ramis caudalibus circ. 8 millim. 
From the long cylindrical form of the body, the numerous 
natatory bristles on the second pair of antennz, and more 
especially the long and narrow cesophagus, together with the 
distinct ventricles, situated in the hinder extremity of the body, 
and from the situation of the ovarium, Leptodora is distin- 
guished from all other Cladocera. With the Polyphemide it 
agrees in not having the body covered with an arched shield, 
but differs in its long cylindrical form. This family appears, 
however, to come the nearest to it, on account of the absence of 
the arched shield, the form of the mandibles, and the absence 
of a branchial appendage to the legs; and, altogether, it would 
seem that the here-described Bythotrephes, Leydig, by reason 
of its long legs and long-extended abdomen, the most nearly 
resembles it. But the Sida or Daphnella brachyura resembles 
it most in the form of the head. I have not found in any 
Cladocer that the digestive canal bore any sign of transition 
to the form here described; but in the Rotatoria we sometimes 
find a similar long and narrow cesophagus, with a distinet sto- 
mach. The ovaria also bore some resemblance to those in the 
Rotatoria. 
In younger individuals (PI. VIII. fig. 2) the abdomen had only 
four segments besides the caudal branches, while in older ones 
there were five. 
The Leptodora moves with a long horizontal spring, but is 
not-remarkably quick. Its extraordinary transparency makes it, 
while living, a particularly interesting object for observation. 
The first time I took it, and placed the vessel in which it was 
kept in the sunshine, I was unable to see the animal itself, but 
its shadow only, when it moved. 
Baron Cederstrém took it in a lake at Bolltorp, in East Goth- 
land ; also in the Ring Lake, in Scania. I have myself taken it 
in the last-mentioned place ; also in the Malar Lake, where it is 
pretty numerous. But it is only found in pure water, and at a 
long distance from the land. 
