DESCRIPTION OF THE PLATES.

FRONTISPIECE.

FIG. 1. Group of Plumatella. The figure to the right is of natural size; that to the left is magnified, and shows one animal contracted and two expanded, with their ciliated tentacles in activity. The group is fixed on a stem of sea-weed.

Edwards.)

(Copied from Milne

2. A Cydippe slightly magnified; the streamers contracted.
3. ▲ Noctiluca Miliaris greatly magnified. The circular spaces are
vacuole, filled with granules of food; these are only temporary,
and are sometimes not visible at all. (Copied from Quatre-
fages.)

4. Group of Clarelling, about three times the natural size, rising
from a creeping stem. The two orifices open and shut rhyth-
mically to suck in and eject water. The lace-work structure
is richly ciliated, and is supposed to represent the gills of the
animal. (Copied from Mr Gosse.)

PLATE IL

FIG. 1. An Eolis coronata.

...

2. A Doris Johnstoni. The two horn-like processes on the head are the antennæ which retract, when the animal is touched, or removed from the water; the coronet at the other end is the circle of branchial plumes.

3. A Pholas dactylus, or rather the shell of one. (Figs. 1-3 copied from Woodward's Mollusca)

4. An Aplysia. The gills are seen under the fold of the skin, to the right. (Copied from Milne Edwards.)

5. A Teredo Norvegica removed from its shell (Copied from Woodward's Mollusca)

DESCRIPTION OF THE PLATES.

PLATE

III.

413

an Actinia, but

a is the base, b

FIG. 1. A diagram intended to exhibit the structure of which must not be taken as strictly accurate. the disk, c the tentacles, d the mouth, e the stomach, f g and k the septa dividing the cavity into chambers, on the free surface of which are the grape-like masses of ovary, and in front of the ovary the convoluted bands. (Copied from Sharpey.) 2. Represents a section of the Actinia as seen in reality. The convoluted bands are seen covering the ovary, and terminating on the inner wall of the stomach. (Copied from M. Hollard.) 3. A magnified view of one convoluted band and ovary, with the mesentery between them, as they appear when unfolded on the glass slide, previous to examination under the microscope. (M. Hollard.)

... 4. Three Thread-capsules from an Actinia, greatly magnified; one with the thread still inside, the other two after the ejection. 5. Vertical section of the Retina of a Perch, showing the relative positions of the pigment layer, the rods and cones, the granules, fibres, and cells. (Copied from H. Müller.)

PLATE IV.

FIG. 1. Campanularia.—The figure to the right is of the natural size; that to the left is a branch greatly magnified. The Polype is seen, flowerlike, expanding itself at the summit. An ovarian capsule, to the right, contains Medusa in various stages of development. (Copied from Van Beneden.)

...

2. Plumularia myriophyllum, natural size. Five of the branches are seen developed into ovarian capsules.

3. Represents the spontaneous subdivision of one worm into two. The head of the second worm is seen formed at the segment where the tail ought to be. (Copied from Milne Edwards.)

PLATE V.

FIG. 1. Lamproglena pulchella, one of the crustacean Epizoa, greatly magnified, and seen from below. The figure is copied from Nordmann, with the addition of the ovisacs, not represented in his plate, but which Burmeister, whose copy I possess, has drawn in pencil. The Lamproglena is found in the gills of a fish (Cyprinus Jeses).

414

DESCRIPTION OF THE PLATES.

FIG. 2. Sagitta Mariana greatly magnified; natural size quarter of an inch. I believe this to be a new species, and I have named it the Mariana. The ova are seen on each side of the alimentary canal; and in the lower half of the body are the cells containing spermatozoa, which issue from the orifices in the fin near the tail. 3. Nymphon gracile (one of the Pycnogonida); natural size. The three circles from which the legs spring convey an inaccurate idea of the reality; they are not cavities, but enlargements of the trunk.

...

4. The same animal in the egg, just before it is hatched; greatly magnified.

FIG.

...

PLATE VI.

1. Syngnathus anguineus (Pipe-fish), about half the natural size. 2. A Comatula rosacea. (Copied from Forbes.)

... 3-10. Development of Strongylus auricularis, one of the Entozoa. Fig. 3 shows the primary germ-cell, surrounded by the yolk; at 4, a division has taken place; 5, a subdivision; 6, still further subdivision; 7, the repeated subdivisions have resulted in what is called the "mulberry mass," out of which the embryo is gradually envoled as in figs. 8, 9, 10. (Copied from Bagge.)

PLATE VII.

FIG 1. Terebella nebulosa removed from its tube. The tentacles are both longer and more numerous than here represented; and the gill-tufts at the side of the head are more apparent. (Copied from Rymer Jones.)

2. An ideal representation of the brain and spinal chord, showing how the nerve-fibres are theoretically supposed to communicate with the nerve-cells of the grey matter of the chord, and thence pass up to the brain, terminating in the cells of the grey matter of the convolutions. (Copied from Leydig.)

3. A Pleurobranchus, natural size, seen from above. ... 4. A stem of the Corkscrew Coralline, natural size.

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