The following Letters apply in all the Plates where they are used to

corresponding parts of the structure :

c.

n.

o.

a. Endocyst.
b. Ectocyst.
b'. Septum of Paludicella.

Invaginated portion of the endocyst.
d'. The proper tentacular sheath.
d. Mouth.
e. Epistome.
d. Orifice in lophophore forming a communication between the

cavity of the epistome and the perigastric space.
f. Esophagus.
f. Cardia.
g. Cardiac cavity of stomach.
g'. Pyloric cavity of stomach.
h. Intestine.
h'. Pylorus.
i. Anus.
k. Lophophore.
1. Tentacula.
m. Calyx.

Retractor muscles of polypide.

Accessory fibres of retractor.
p. Rotatory muscles of tentacular crown.
9. Tentacular muscles?

Elevator muscle of epistome.

Anterior parieto-vaginal muscles. t. Posterior parieto-vaginal muscles.

Parietal muscles.
w. Nervous ganglion.

Nervous filament to lophophore.
'. Nervous filament passing round the lophophore.
y. Nervous filament to esophagus.

Statoblast.
0. Funiculus.
e'. Superior funiculus of Paludicella.

Hepatic layer of stomach.
1. Middle layer of stomach.
11. Internal layer of esophagus.
12. Internal layer of rectum.
ps.

External layer of stomach.
ut External layer of esophagus.
m2. External layer of rectum.
E. Spermatozoa.
p. Gemma.
X:

Testis.
Ovary.

8.

DESCRIPTION OF THE PLATES.

PLATE I.

CRISTATELLA MUCEDO.

Fig. 1. Cristatella mucedo ; an adult specimen, adhering to the submerged stem of Ranunculus

aquatilis. Of the natural size. 2. The same enlarged. 3. Statoblast of Cristatella mucedo in an early stage; it is surrounded by a ciliated mem

hrane, and there is as yet no appearance of the marginal spines. 4. The same more advanced; the enveloping membrane is destitute of cilia, and the spines

have begun to grow out from the margin of the disc. 5. The same, still further advanced ; the spines have impinged on the enveloping mem

brane. 6. The mature statoblast; the enveloping membrane has been torn by the pressure of the

spines, and has disappeared, and the statoblast has become free. 7. The same, viewed on the edge. Figs. 3—7 are magnified about 50 dia meters. 8. Natural size of mature statoblast.