In size, the tribe before us extends through a wide range, from that lovely little gem, the Turris neglecta, that looks like a bead of red coral no larger than a hemp-seed, to the massive Rhizostoma, which frequently finds its way into our southern harbours, the disk of which resembles in dimensions a lady's parasol. In general, the smaller kinds belong to the Naked-eyed division, the larger to that characterised by Covered eyes. These terms are convenient formulæ to express distinctions, which, while they include the organs of vision, do not rest wholly on them, the characters in question being found associated with others which unitedly indicate the latter as a higher grade of organisation than the former. In the one, the margin of the disk bears wart-like eyes, which are protected by complex folds or veils of membrane; and this circumstance is associated with another of great importance, the presence of a much ramified and anastomosing series of vessels. In the other division, the eyes, when present, are of simpler structure, quite naked; and the vessels are simple canals, usually unbranched, and never anastomosing. To the former group, the Covered-eyed Medusa, no more than about ten species are assigned as natives of the British seas; and these have as yet found no special historian. Of the latter, Professor Forbes, in his beautiful "Monograph of the British Naked-eyed Medusa," has enumerated forty-three species, arranged in eighteen genera, and several more have been added since the publication of that work. We shall take the liberty of quoting from it a few practical directions for procuring these lovely creatures, and the more willingly because we have, by personal experience, proved their efficacy :

F

"They are to be sought for in summer and autumn when the weather is warm and dry, and the sea calm and clear. They abound within reach, mostly in the afternoon and toward nightfall,-probably, also, during the night, though not then so near the surface of the water. A small bag of fine muslin, attached to a metal ring, is the best instrument by which to take them, and may be used either as a land-net fixed to the end of a stick or pole, or as a tow-net suspended over the stern of a vessel, when at anchor, or making very gentle way through the

"When the tow-net is taken out of the sea it is to be carefully reversed, and its contents gently emptied into a basin or glass jar, filled with clear salt-water. It is best to plunge the net beneath the surface when being emptied, as thus the Medusæ are enabled to detach themselves from the threads and swim away without injury. When the net is out of the water they appear like little, adhering, shapeless, masses of clear jelly, and exhibit no traces of their elegant form and ornaments. When in the jar or basin they are often, on account of their extreme transparency, very difficult to distinguish; but by placing the vessel in the sun or beside a strong artificial light, we see their shadows floating over the sides and bottom of the basin, like the shadows of flitting clouds on a landscape. These soon guide us to the creatures themselves, and before long we distinguish their ocelli and coloured reproductive organs;"*-when they may be lifted into other vessels,the larger by means of a spoon, the smaller with thumbtubes, for more close examination.

*Op. cit., p. 89.

CHAPTER IX.

ACALEPHE (Sea-blubbers).

Continued.

WE propose now to speak of the reproduction of the Medusa, at least of the Discophora, or umbrelliform families, for of the other orders we know little, except their forms. Some of the phenomena of Alternate Generation have been described in a previous paper, a compound hydroid Polype giving birth to tiny Medusa, which afterwards produce a generation of Polypes. We have now to contemplate the counterpart of this wonderful process,-a free swimming Medusa producing gemmules, or motive eggs, each of which becomes a stationary Polype, and ultimately throws off a number of Medusa.

The ovaries in these animals are ordinarily placed in contact with the walls of the central stomach, or with the digestive canals that radiate from it across the disk. At the season of development they consist of numerous ribands of membrane, much folded and convoluted, and fringed with free pendent filaments, covered with vibratory cilia. The ova are globose, gelatinous germs, existing in immense multitudes, which on extrusion are strongly ciliated, and bear a close resemblance to Infusorial Animalcules. They

are endowed with the power of spontaneous motion, and apparently of choice as to locality, and have a definite form, which is commonly pear-shaped, though the outline is very flexible and variable.

As the time of oviposition approaches, the umbrella becomes gradually reverted, or turned inside out, the ovaries swelling and protruding more and more, until they occupy the principal portion of the animal. We believe this to be general in the discoid Medusa, having observed it in species that belong both to the Covered and Nakedeyed divisions-namely, in the genera Chrysaora, Pelagia, and Turris.

In the case of the lovely little Coral-bead Medusa (Turris neglecta), already alluded to, the phenomena are well seen, the ovaries being orange or pale scarlet, studded with proportionally large ova, of a rich purple hue. The latter appear to escape from the walls of the ovaries, working their way out at the sides. They drop down on the bottom of the vessel, where they move about slowly for a while, but to no great extent, by means of their vibratile cilia. By watching them we ascertain the following facts. The gemmule, having adhered to some foreign substance, grows out into a lengthened form, variously knobbed and swollen, and frequently dividing into two branches, the whole adhering closely to its support. After a day or two's growth in this manner, a perpendicular stem begins to shoot from some point of this creeping root, and soon separates into four straight, slender, slightly divergent tentacles, which shoot to a considerable length. The whole is of a crimson hue, with the exception of the growing extremities of the creeping root, which are pellucid white.

The little creature is now a polype of four tentacles. We have not been able to trace the development further in this species, but the deficiency has been supplied by the observations of others upon the larger genera.

The most common-or, at least, the best known-Medusa in the British seas is the Aurelia aurita, that Seablubber, with four imperfect rings of pink in the disk, which is so often seen floating in our harbours, or washed ashore on our beaches. In this species the whole progress of development, from the first appearance of the ova to the formation of perfect Medusa, has been traced by several observers, and the following is an epitome of the highly curious facts.

The pink semi-rings are the ovaries, in which the ova are first developed. At a certain early stage they are transferred to four pouches beneath the arms, where they increase in size, become granular in texture, and at length assume the figure and manners of an oblong Infusorium. As each one quits the maternal pouch, it swims freely away by the aid of its investing cilia, with its larger end foremost. Soon, however, it selects a place of rest, to which it adheres by its smaller extremity, and quits the roving for the stationary life.

A depression now forms in the thicker end, which deepens and becomes a digestive cavity; while the margin expands and buds out into four processes, which are strongly ciliated. Up to this time it had been yellowish and opaque; it now becomes colourless and transparent. Four other processes are now formed in the interspaces of the former four; so that the little animal now closely resembles a Hydra with eight tentacles, especially as these