PACKARD.] MOEPHOLOGY OF PHYLLOPODA. 395 



homologized with the autennfB, being true appendages. This is especi- 

 ally seen in the cockroach and in Mantis tessellata (Guide to Study of In- 

 sects, p. 17, fig. 23). 



TJie cercopoda. — We would suggest the name cercopoda* for the 

 caudal appendages of the Phyllopoda, which are outgrowths from the 

 telson. There seems to be no such appendages of the telson or anal 

 arthromere in the Malacostracous Crustacea, as the uropoda are devel- 

 oped on the segments anterior to the telson. But when we turn to the 

 Entomostraca, we see that they occur, as a rule, in all Copepoda, where, 

 in some genera {Pontellina, Zaus, Thalestris). they are two-jointed. 

 These appendages then, in Copepoda, are true jointed appendages, arising 

 from the end of the terminal segment of the urosome, and thus forming 

 the last pair of abdominal appendages. In the order Branchiopoda 

 the cercopods of the Copepoda are represented by the moveable, curved, 

 slender, terminal claw of the telson ; and this form ]iersists in the 

 higher Limnadiadce (Plate III, fig. 7; Estheria, Plate XXV, figs. 5, G), 

 being absent in Livmetis. The long, jointed, style-like caudal ax)pend- 

 ages of Apus are also the homologues of the Copepodous cercopoda, 

 as well as of the Limnadiad claw-like appendage. In the larva, as seen 

 by Dr. Gissler's drawings, fig. 8, Plate XXXV, they are short and broad, 

 and their cavity is continuous with the body-cavity. Late in larval life, 

 as seen in fig. 9 of the same plate, a joint appears, and later on in adult 

 life the cercopoda of the Apodidw, as seen in Plate XVI, aie nearly per- 

 fectly jointed, with short, stout sette arising from the edge of each joint. 



In the cercopoda of the Branchiopods we have reproduced quite ex- 

 actly those of the Copepoda. So it appears that these appendages are 

 restricted to the Entoniostracous Crustacea, although they are also a 

 characteristic feature of the Phyllocarida. 



Histology of the postoral appendages. — The male hands of the first 

 pair in Estheria and Limnadia present some peculiarities of interest. 

 The finger-like two-jointed fifth endite of Estheria mexicana (Plate XXV, 

 fig. 3a, l^) is traversed by a thick nerve, which appears to originate 

 from a multitude of nerve-cells, almost completely filling the distal joint. 

 The latter when magnified by a Tolles ^ A eye-piece (fig. 3c) is seen to 

 be filled with rather large nerve-cells {g c), whi(;h are arranged serially. 

 Between the rows of cells are apparently fine nerve-fibers, which have 

 not been so distinctly indicated by the artist as in my original drawing. 

 These fine fibers appear to arise near the terminal cells (r/ c) and prob- 

 ably originate in the seven setiB at the end of the joint. It is plain that 

 this endite is the sensitive portion of the hand, though whether it is of 

 any special sense and other than tactile may seem doubtful. 



In Estheria compleximamis (Plate XXIX, fig. 5) and in the same joint 

 of the fifth endite of the first i)air of hands, when magnified by the 

 same power (| Tolles A), the main nerve is seen to traverse the joint, 

 passing through a great number of very large nerve or ganglion cells 

 (^c), which are not, however, arranged serially as in E. mexicana. The 

 nerve appears to break up into a number of fibers which probably in- 

 nervate the numerous fine cilia-like setse at the end of the finger-like 

 appendage. 



In the first pair of legs of Estheria compleximanus (Plate V, fig. 7) the 

 sixth enditeis provided with nerve-cells and nerves which supply the setcTe, 

 as seen in Plate XXIX, fig. 3. Here the ganglion-cells are contained 



* We should also apply this name to the jointed anal stylets of insects sncli as tlie 

 cockroach, Mantis, and other Orthoptera and Pseudoueuroptera, as well as tlie dipte- 

 rous Chrysopila, and numerous other forma. 



