1883.] Zoölogy. 883 
us as to the arthropodan nature of their teeth, but Professor 
Moseley’s earlier memoir on the development of Peripatus, ap- 
pears to us to indicate that they are the branch-homologues of the 
mandibles of Arthropoda, the mouth-region of the adult Peri- 
patus being somewhat degenerated as compared with the embry- 
onic structure. 
We have here also interesting descriptions of the histology of 
the (for an Arthropod) strangely arranged nervous system, with 
its two widely separated nervous cords. The account of the 
trachez corroborates, in the main, Professor Moseley’s earlier 
account. Says Balfour: “The apertures of the tracheal system 
are placed in the depressions between the papilla or ridges of 
the skin. Each of them leads into a tube, which I shall call the 
tracheal pit (Fig. 30), the walls of which are formed of epithelial 
cells bounded towards the lumen of the pit by a very delicate 
cuticular membrane Foniatsui with the cuticle covering the sur- 
face of the body. * Further investigation proved that 
the trachee mai sii from the. slightly swollen inner ex- 
tremity of the narrow part of the pit, the expanded walls of the 
pit forming ~ pr pruneniat ep covering for the diverging bundles 
of trachez. The trachez themselves are Regge! 
minute, EN ii far as I could follow them) tube ch 
opening by a separate aperture into the base of the tradida pit, 
and measuring about 0.002™" in diameter. They exhibit a faint 
Sada hg siratan which I take to be the indication of a spiral 
fiber. Moseley states that the tracheæ arise from the 
skin ‘all over the surface of the body, but are especially developed 
in certain regions. He finds a ‘row of minute oval openings on 
the ventral surface of the body,’ the openings being ‘ situate with 
tolerable regularity in the centers of the interspaces between the 
pairs of members, but additional ones occurring at irregular in- 
tervals. Other similar openings occur in ve yeebeieng on the inner 
side of the conical foot protuberance.’ * There is a 
considerably more numerous than the legs. ` There is also a dou- 
e row of openings, again more numerous than the legs on each 
side of the median ventral line between the insertions of the legs. 
Moseley speaks of a median row in this position. I think this must 
be a mistake. * * * Both the dorsal and ventral rows are very 
irregular.” A considerable number of openings were found around 
the base of the feet, and the dorsal rows of tracheal apertures are 
aan keg into the head and give rise to enormous bundles of 
trac 
he body-cavity is formed of three compartments—one central 
and two lateral, the latter containing the “segmental organs,” 
which are regarded as probably of an excretory nature and homol- 
bony with the nephridia or segmental organs of the Chatopod 
worms. 
