but his observation has not been verified by subsequent investigations. According to Milne Edwards, followed by others (among whom I must include myself), the nervous system consists of a ganglion, situated at the aboral pole of the body, whence nerves radiate, the most conspicuous of which are eight cords which run down the corresponding series of paddles; and a sensory organ, having the characters of an otolithic sac, is seated upon the ganglion. Agassiz and Kölliker, on the other hand, have denied that the appearances described (though they really exist) are justly interpreted. And again, though the body, described as an otolithic sac, undoubtedly exists in the position indicated in all, or most, of the Ctenophora, the question has been raised whether it is an auditory or a visual organ.
These problems have been recently reinvestigated with great care, and by the aid of the refined methods of modern histology, by Dr Eimer,[1] who describes a nervous system, consisting of extremely delicate varicose ultimate nerve fibrils, which traverse the mesoderm in all directions, and are connected here and there with ganglionic corpuscles. These nerves are only discernible with high magnifying powers, as they are for the most part isolated, and are collected into bundles only beneath the longitudinal canals. The mass which lies beneath the lithocyst is composed of cells, but these have none of the special characters of nerve cells. Eimer states that he has traced the filaments, which he considers to be nerves, into direct continuity with muscular fibres; and, around the mouth, into subepidermal bodies, which he regards as rudimentary forms of tactile corpuscles. The lithocyst is recognised as an auditory organ, and, in addition, eye-spots are described.
With a fundamental similarity of organisation, the form of the body varies extraordinarily in the Ctenophora. One of the genera which is commonest on our coasts—Cydippe (Pleeobrachia)—is spheroidal; others (Beroë) are more ovate; others are provided with large lobular processes (Eucharis), while an extreme modification, in which the body is ribbon shaped, is seen in Cestum.
The Ctenophora are divisible into two very unequal groups:[2]
I. Eurystomata, in which the large oral aperture occupies the truncated extremity of the oval body.
1. Beroidæ.
II. Stenstomata, in which the oral aperture and the gastric sac are small relatively to the size of the body.
2. Saccatæ.
3. Lobatæ.
4. Tœniatæ.
1. Beroïdæ.
The body is ovate, truncated at the oral pole, the aboral being more or less acuminate and mobile. The digestive cavity occupies a large portion of the body. The oral margin is simple in Beroë and Idyia; but in Rangia the interradial spaces are notched, and in each a short process projects. The radial canals are connected by a circumoral canal. No tentacles are present. The ctenophores of Pandora do not extend over more than half the body, as in the embryos of Cydippe. The development of the Beroidæ is unaccompanied by metamorphosis.
2. Saccatæ.
The circumoral canal is absent. The oral aperture is laterally compressed, its long axis being at right angles to the plane of the tentacles, which are present in all the genera, and which are either simple (Cydippe), or furnished with lamellar and filamentous appendages (Hormiphora). The ctenophores are equal in length, or the lateral ones are fully developed, while the intermediate are shorter.
3. Lobatæ.
The oral and aboral pole, or the oral only, bear lobate appendages. Boliná has a pair of oral lappets, into which the radial canals are prolonged. The ctenophores corresponding to these lobes are the longest, while the middle ones are much shorter, and are prolonged on to an auricle or finger-like lobe. The tentacles are represented by a tuft of short processes on either side of the mouth. The young Boliná has the form of Cydippe, and like it bears a pair of long-fringed tentacles. The aboral region, bearing the lateral ctenophores, grows more rapidly than the oral, so as ultimately to project in two principal lobes, by which the similar outgrowth of the median aboral regions with its ctenophores is arrested, the auricles being the dwarfed representatives of these regions. These auricles in Eucharis are longer, so that the ctenophores are all of equal length. The tentacles of this genus are placed at the oral pole; the oral lobes are equivalent to the median ctenophores of Cydippe. Eurhamphæa has the oral lobes small, the body elongated, terminated by two conical projections, on which the median etenophores are prolonged.
4. Tœniatæ.
The body of Cestum is laterally compressed and elongated in a direction which corresponds to one of the transverse diameters of Cydippe, the ribbon-like band thus formed being sometimes three or even four feet long. The tentacles are near the oral pole; the canals are ten in number; the medio-lateral canals terminate in trunks which follow the oral margin of the ribbon, and thus correspond to the circular canal of Beroë.
Many Actinozoa (Pennatulidæ, Ctenophora) are phosphorescent; but the conditions which determine the evolu tion of light have not been determined.
All Actinozoa are marine animals, and the distribution of many of the families (Actinidæ, Turbinolidæ, Pennatulidæ, Beroïdæ) is extremely wide, and bears no ascertainable relation to climate. (T. H. H.)
Action, in Law, is the process by which redress is sought in a court of justice for the violation of a legal right. The word is used by jurists in three different senses. Sometimes it is spoken of as a right—the right, namely, of instituting the legal process; sometimes, and more properly, it means the legal process itself; and sometimes the particular form which it assumes. The most universally recognised division of actions is the division established by the Roman lawyers into actions in rem and in personam. An action in rem asserts a right to a particular thing as against all the world; an action in personam asserts a right only as against a particular person. For the sake of convenience, the law relating to actions ought to form a separate section by itself in a properly constructed code.
In Roman law the action passed through three historical stages—
In the first period, which was brought to an end by the Lex Æbutia, about 573 A. U. C., the system of legis actiones prevailed. These were five in number,—the actio sacramenti, per judicis postulationem, per condictionem, per manus injectionem, per pignoris captionem. The first was the primitive and characteristic action of the Roman law, and the others were little more than modes of applying it to cases not contemplated in the original form, or of carrying the result of it into execution when the action had been decided.
Action, in English Law, means the form of civil process hitherto observed in the Courts of Common Law. The procedure in the Court of Chancery is totally distinct, but some account of the former may be desirable in order to explain the new form of action introduced for all the civil courts by the Judicature Act of 1873:—
