PACKARD.] INTERNAL ANATOMY OF PHYLLOPODA. A401 
however, nucleus-like bodies occur on the points of intersection, I have 
not yet been able to discover. In the profile view of the animal the 
central body appears exactly as in the Daphnide, in the form of a clear 
round vesicle in the feeble (matten) brain-substance, and can thus give 
ready opportunity for illusion. An independent vesicle, such as Claus 
describes in Daphnia magna, I have not seen here. 
‘Krom the lateral lobes of the supracesophageal ganglion arise the 
following 5 nerve-pairs: 
“1, The large optic nerve. 
“2. Several nerve-twigs to the eye-muscles. 
«3, A slender fiber on each side to the frontal organ. 
“4. First antennal nerve. 
“5, The ‘ hirnschenkel,’ 
“From the middle division arise only 3 paired and an unpaired 
nerve, Viz: 
“6, An at least externally unpaired nerve, and 
“7, A paired nerve-stem, both to the so-called larval eye. 
“8. An outermost fine fiber on each side, which arises laterally from 
the seventh pair, and goes above and outside of it. 
“9, A slender pair of nerves to the csophageal musculature. 
‘‘Of these nerves Zaddach (Apus) knew only those mentioned under 1, 
4,5, 7, and 9, but as they occur also in Branchipus as well as in several 
Cladocera investigated by me, there can be no doubt that they are pres- 
ent also in Apus, ‘and were overlooked by him.” 
Spangenberg then describes the ganglion opticum and eye. 
Ventral ganglion chain.—The second cephalic or first ventral pair of 
ganglia, which lie on the side of the esophagus, are the second antennal 
ganglia. This ganglion, and the 2d antennal nerve which arises from 
it, is figured by Klunzinger. 
Then follows the mandibular and then the maxillary ganglia. These 
are succeeded by 22 pairs of ganglia. 
There is probably no essential difference between the nervous system 
of Hstheria and Limnadia. From anumber of sections of Hstheria mex- 
icana kindly made for us by Mr. N. N. Mason, we have drawn figures 
1, 2, 4, and 5, Pl. XX XIII, which partly illustrate some points in the 
structure of the nervous system. Fig. 2 represents a section which evi- 
dently passed through the brain (br). It is seen to be a double ganglion, 
with the hemispheres more distinctly marked than in Grube’s meinen 
tion of that ot Limnetis. Fig. 1 and the enlarged view, Fig. 4, passes 
through a ganglion, which we take to be the brain. The section must 
have been very oblique, as the cesophagus is seen to appear as if situ- 
ated above the brain. The section passes through the larval ocellus, 
whose cones and pigmeut mass have still survived, though sunk out of 
sight under the integument. 
‘Fig. 5 represents a ganglion posterior to the maxillary ganglion, and 
probably supplying the nerves to the first pair of feet, and situated 
directly under the intestine, the epithelium of which is shown in the 
figure. The histological structure is seen to be very simple. The gang- 
lion consists of scattered ganglion-cells and fine granules, which may be 
the ends of fibers, but no distinct fibrous structure was to be detected. 
The brain, fig. 4 br, and fig. 2 br, is apparently no more complex in 
its histological structure than the ventral ganglia. 
A good ‘deal of time was given to attempts to work out the nature of 
the brain, but though Mr. Mason very kindly made sections of a number 
of specimens of Ls stheria, Apus, and different fresh Branchipodide, yet 
owing to the inherent difficulties in the nature of the investigation very 
26 H 
