Fig. 1. 
Fig. 2. 
Fig. 3. 
Fig. 1. 
Fig. 2. 
Fig. 5. 
Fig. 1. 
Fig. 2. 
Fig. 3. 
MUSEUM OF COMPARATIVE ZOOLOGY. 239 
PLATE II. 
Upper portion of a taster of Nanomia, showing the so-called oil globule 
forming a protuberance on one side. The tentacle is not represented. 
Four nectocalyces of Nanomia, showing their mode of fitting together. 
The stem is shown through the sides of the “horns,” or gelatinous 
extensions of the nectocalyx. The sinuous tubes are the lateral chym- 
iferous vessels. The radial tubes, which pass directly, without a sinu- 
ous course, from the tube which joins the system to the stem, are not 
shown. 
Halopsis ocellata (side view). 
PLATE IV. 
A fish (Seriola zonata) with Hydrichthys attached to its side and anal 
region. 
Single cluster of gonophores separated from attachment to the basal plate 
by which the whole colony is united to the fish. The attachment is at 
the lower end. Medusa buds in various stages of development are 
shown at the ends of the lateral branches. Each attached colony has 
a large number of bodies like Fig. 2 scattered irregularly on the basal 
plate. The structure represented in Fig. 2 is described as the gono- 
some of Hydrichthys. 
. Single filiform body of a Hydrichthys colony. 
Section (optical) of a medusa bud of Hydrichthys. The two projections 
on the left are the opposite tentacles, which have an internal cavity 
communicating with radial tubes, two of which are represented. The 
two spurs from this cavity which arise near the bases of the tentacles 
are the beginnings of the circular canal. The large cavity at the centre 
of the bell is the cavity of the proboscis. The slit-like cavity separated 
from the cavity of the proboscis by the thick layer and the thin layer 
which lines the former, is the future bell cavity. 
Enlarged end of the filiform body of Hydrichthys, showing the orifice open 
and a round mass (food *) in its cavity. 
PLATE V. 
Adult medusiform gonophore of Hydrichthys with four tentacles (side 
view). This medusa was raised from the hydroid, and is supposed to 
be not much younger than the adult. _ 
An immature medusa of Hydrichthys found in the aquarium on the morn- 
ing after capture. Raised from the Hydrichthys in countless num- 
bers. (Side view.) 
View of the last-mentioned from actinostomal region. This medusa is 
a very little younger than Fig. 2, since the two stumpy tentacles have 
not yet begun to appear. 
