twenty times as long as the animal, and clothed at its upper part by about forty scattered tentacles, which twine about in most violent motion. The animal seems to be constantly searching the water around for prey, and occasionally to press the tentacles firmly against the body of the proboscis, as if to imbed some matter into the soft substance of the latter the usual mode of feeding amongst the Acinetiens, to which class it belongs. It is impossible not to be struck by the extreme similarity in outward form between this animal and the Echinoderm Sipunculus Bernhardi. In both animals occur the same shapeless body, the same entirely retractile proboscis crowned with tentacles, and the same peculiar motions in seeking for prey. But with the form, the similarity ends, for the Echinoderm possesses a highly organised structure, while in the transparent Protozoon no structure at all has been detected.

(2.) On Hermaphrodite Reproduction in Chrysaora hyoscella. (Plate IX).-Professor Allen Thomson, in his "Treatise on the Ovum,"* states that "the Discophora (Medusa) are of distinct sexes." I have found this to be the case in all the Steganophthalmata and Gymnophthalmata which I have examined, with the exception of the subject of this notice.

Large individuals of C. hyoscella are hermaphrodite; but smaller ones are found which are unisexual, the male or female element being suppressed, as in some diœcious plants.

The best method of examining the structure of the reproductive apparatus of this animal is to place the Medusa, in its natural position, in a large basin of sea-water. The umbrella, all but its margin, is then to be cut away. The cavity of the stomach is thus laid open, and we have a good view of the interior aspect of the sub-umbrella. We find that each lip of the mouth divides, at its insertion, into three pillars. The central pillar projects as a large rounded bulb into the stomach, while the lateral ones diverge, pass outwards towards the margin, and afterwards converge and unite together, so as to form, with the bulb of the central pillar, the thickened opening or framework of the ovarian * Cyclopædia of Anatomy and Physiology, vol. v. p. 129, "Acalephæ."

PLATE IX.

α

a

6.

c b

d

d

T.Strethill Wright, del.

J.Pasire.Sc.

1-5 Reproduction of Chrysaora. 6. Reproduction of Truncatulina.

pouch. This opening is closed by the ovarian membrane, which consists of three layers-1. the endoderm, or intestinal layer; 2. the gelatinous layer; and 3. the ectoderm, or dermal layer. The ovarian membrane appears as a flocculent mass, from its being corrugated into numerous folds. By injecting air beneath it, it becomes inflated, and the folds are opened out. It then presents the appearance of a large transparent bag traversed by flat convoluted bands. These bands are the ovaries, and contain, between their endoderm and gelatinous layer, countless ova and planuloid larvæ in various states of development.

The ova of C. hyoscella do not present, at any stage, a trace of germinal vesicle or spot-objects which are so readily detected in the ova of other polypoid zoophytes.

The planuloid larvæ resemble those of Medusa aurita; but the polyps into which they become developed approach more closely to the Lucernarian type, in having a pedicle which is surrounded by a gelatinous covering, and at its foot by a horny corallum, which I have described and figured elsewhere.*

The structure and position of the male organs are remarkable. Attached to the inner surface of the ovarian membrane by delicate pedicles, and projecting into the stomach, are numerous large grape-like bodies of translucent "jelly," accompanied in many cases by fringes of tentacles of the same substance (Plate IX. fig. 1). The surfaces of the first bodies are dotted with minute papillæ, and on the tentacles are found tubercles or thickenings covered with similar papillæ. These papillæ are spe m-sacs filled with spermatic cells and spermatozoa (fig. 4). Smaller bodies, about the size of a hemp-seed, and specked with spermsacs, also occur attached to various parts of the lining membrane of the stomach, and even to that of the lips or long oral tentacles, down to the very tips of those organs.

The small Chrysaoras (about 4 inches in diameter) have no ovarian bands in their pouches, which only contain masses of the grape-like bodies and tentacles before mentioned. These tentacles are not homologous with the minute, hol* Edinburgh New Phil. Journal for 1859.

VOL. II.

2 F

low, cnidophorous or sting-cell-bearing tentacles found on the inner surface of the ovarian membrane of Medusa aurita and Lucernaria auricula; they are simply, as are the grapelike bodies, prolongations of the endoderm and gelatinous layer of the ovarian membrane.

Although the testicles of Chrysaora are apparently not homologous with those of other zoophytes, yet in reality they differ but little from those of Actinia and Lucernaria. I have given, in Plate IX. fig. 2, a section of the testicle of Chrysaora, and in fig. 3, of one of the same bodies in Actinia mesembryanthemum. In Chrysaora, the thin endoderm (a) forms the distant sperm-sacs which project from the surface. In Actinia, the thick endoderm (a) also forms the more closely aggregated sperm-sacs, and fills up the interstices between them. The testicle of Lucernaria, again, resembles in shape and structure fig. 3; but the sperm-sacs are so closely moulded together, that they form hexagonal prisms divided from each other by exceedingly delicate walls of endoderm.

The sperm-sac of Chrysaora (fig. 4), as well as of other Steganophthalmatous Medusa, Lucernarias, and Actinias, is thus always formed of the endoderm or lining membrane of the digestive system, while the sperm-sac of Hydra (fig. 5), the Hydroid Polyps, and the Gymnopthalmatous Medusæ is formed of the ectoderm. In the first class of animals the spermatic cells (fig. 4) become first matured into spermatozoa in the centre (c), or at the base of the sperm-sac, the part most distant from the endoderm (a). In the second class they ripen at the periphery, or at the summit of the sperm-sac (fig. 5), the part also most distant from the endoderm (a).

My friend Mr Hincks, in his valuable paper on " Clavatella,"* appears to consider that the ova of that creature may be developed from the ectoderm. But an examination of the embryology of a very large number of zoophytes forbids me to entertain this idea. The endoderm of the generative capsule in these creatures consists of two layers intimately connected with each other. The external layer, or that in * Annals and Magazine of Natural History for February 1861.