MUSEUM OF COMPARATIVE ZOOLOGY. 9 
just described for Urnatella has been described and figured by Ehlers 
for Ascopodaria. Such a highly complicated septum seems indeed 
to be common to the Pedicellinid&, which in this respect appear more 
nearly allied to Urnatella than does Loxosoma, in which such septa are 
absent. 
In Pedicellina Benedeni also, which has a segmented stalk, the seg- 
ments are separated from one another, according to Fottinger (87, 
pp. 301—303), by perforated septa. 
2. The Calyx. 
Under this heading I shall treat successively of the body wall (includ- 
ing the lip of the atrium, and the tentacles), the atrium, the alimentary 
tract, the body cavity, the nephridia, the sexual organs, and the nervous 
system. 
A good idea of the external form of the expanded calyx may be gained 
from Leidy’s figures. My own, having been drawn chiefly from preserved 
material, show the polypide for the most part in a retracted condition 
(cf. Plate I. Fig. 2). When thus retracted, the atrial opening does not 
lie at the apex of the calyx, but is thrown sharply over towards the oral 
aspect (Plate III. Fig 18). 
The body wall is composed of a single layer of excessively thin epi- 
thelium, — the ectoderm, — which has secreted a thin cuticula. This 
cuticula is thickened in places, producing papilla, which are irregularly 
scattered over the calyx. At the lip of the atrial opening, as the pas- 
sage into the atrium in the retracted condition may be called, the ecto- 
derm is thicker than elsewhere, and folds back upon itself until it reaches 
the base of the lophophore. This backward-reflected portion I shall 
call by the name kamptoderm, for although its homology with the kamp- 
toderm of Ectoprocta may not be entirely beyond doubt, I cannot see 
any important difference between the two structures, either in their adult 
relations or in development. As in the Ectoprocta, so here the polypide 
is formed in the retracted state, and the atrial opening does not break 
through until a late stage is reached. 
In Ectoprocta the line of union of the kamptoderm and body wall, 
i.e. the lip of the atrial opening, is marked by a thickened ring com- 
posed of elongated ectodermal cells, at the base of which lie the fibres of 
a sphincter muscle. This organ constitutes the * Randwulst ” of Phy- 
lactolemata or the “ Diaphragma” of Gymnolemata. Does an organ 
homologous with this occur in Urnatella? Tt is in keeping with the 
more primitive organization of the Endoprocta that, although a corre- 
