PACKARD.] INTERNAL ANATOMY OF PHYLLOPODA. 397 
nerve-cells (nc!). There is in each set but a single submarginal and a 
marginal nerve-cell (nc). The two cells are connected by a broad 
nervous tract, and beyond the marginal cell the setal nerve continues 
into the base of the sete. 
In the sixth endite of the first pair of feet of Thamnocephalus platyurus 
the arrangement of the ganglion-cells differs somewhat from the other 
Branchipods described. As seen in Plate XXIX, fig. 8, there seems 
to be no marginal ganglion-cells, but a much larger number of sub- 
marginal cells, which are arranged serially, the outer row of the sep- 
arate nerves forming a quite regular series parallel to the edge of the 
endite. The tactile nerves (tn) containing these ganglion cells pass 
into the sete. There is also to be seen a submarginal row of minute 
sete. The same histological nervous structure is seen in one of the 
smaller endital lobes, 7. e., the fourth (Plate X XIX, fig. 7). A nerve 
here evidently leads from the axis of the leg, and enlarges before reach- 
ing the large mass of ganglion-cells (gc) from which the setal nerves 
arise. It will be seen that the ganglion-cells are of the same size and 
appearance as in the end of the finger of the male of Hstheria complex- 
amanus (fig. 5). 
The base of the flabellum of Thamnocephelus, as of all the genera in 
the family, are filled with large cells, rich in fat granules, as seen in 
Plate X XIX, fig. 8b; while the polygonal cuticular cells of the flabel- 
lum are represented at fig. 8a. 
NOTES ON THE INTERNAL ANATOMY OF THE PHYLLOPODA. 
Tt was not the author’s design to make a special investigation of the 
internal anatomy of the Phyllopods, and the following notes on Amer- 
ican species should only be regarded as supplementing what has been 
already published by Zaddach, Grube, and Spangenberg, which we 
have consulted and of which a résumé will be found in Gerstaecker’s 
Arthropoden. 
The general anatomy of Limnetis observed in ZL. gouldii while alive 
does not differ in any important respect from that of Limnetis brachyura, 
well figured by Grube, whose figure I have reproduced on Plate 
XXXII, figs. 6-8. The form and topographical relations of the digest- 
ive canal with the liver, and of the heart are the same in our species as 
Grube represents. 
Cur fig.6 on Plate XXVI represents the structure of an ovarian 
lobe of Limnetis gouldii. The mass is filled with ovarian nucleated cells. 
The digestive system.—An undeviating characteristic of the Phyllo- 
pods is the relation of the liver to the stomach and the peculiar way in 
which it is packed away in the head-cavity, enveloping the brain and 
filling the frontal cavity of the Limnadiada and of Apodide. The only 
other Crustacean except the Branchipods which have this characteristic 
is Limulus, and in this respect this animal closely resembles the Phyl- 
lopods. 
In Limnetis the mouth (Plate XX XI, figs. 6, 8) is situated between the 
mandibles, as seen in our copy of Grube’s figure, and the duct of the 
liver (Fig. 8, liv.) is seen to enter the digestive tract very near the short 
cesophagus. 
In Estheria mexicana Plate XX XIII, fig. 2, shows the relation of the 
lobes of the liver to the common duct, and the connection of the latter 
with the rather large stomach. The cavity of the head is capacious, 
and filled with the convoluted lobules of the liver, of which transverse 
and longitudinal sections are shown in the figure. Tig. 2a is a still 
