PACKARD.] INTERNAL ANATOMY OF PHYLLOPODA. 397 



nerve-cells (wc^). There is in each set but a single snbmarginal 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 setae. 



In the sixth endite of the first pair of feet of TliamnocepTialus 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 (<w) containing these gangbon cells pass 

 into the setse. There is also to be seen a submarginal row of minute 

 setse. The same histological nervous structure is seen in one of the 

 smaller endital lobes, i. e., the fourth (Plate XXIX, 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 JEstheria co^nplex- 

 imanus (fig. 5). 



The base of the flabellum of Ihamnoceplialus, as of all the genera in 

 the family, are filled with large cells, rich in fat granules, as seen in 

 Plate XXIX, fig. 86; while the polygonal cuticular cells of the flabel- 

 lum are represented at fig. 8 a. 



NOTES ON THE INTERNAL ANATOMY QF THE PHYLLOPODA. 



It 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 resume will be found in Gerstaecker's 

 Arthropoden. 



The general anatomy of Limnetis observed in L. gouldii while alive 

 does not differ in any important respect from that of lAmnetis hrachynra, 

 well figured by Grube, whose figure I have reproduced on Plate 

 XXXI, 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. 



(Jur fig. 6 on Plate XXVI represents the structure of an ovarian 

 lobe of Limnetis gouldii. The mass is filled with ovarian nucleated cells. 



Tlie 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 Limnadiadce and of Apodidce. The only 

 other Crustacean excej^t the Branchipods which have this characteristic 

 is Limulus, and in this respect this animal closely resembles the Phyl- 

 lopods. 



In Limnetis the mouth (Plate XXXI, 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 

 oesoj)hagus. 



In Estheria mexicana Plate XXXIII, 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. Fig. 2a is a still 



