Page:Encyclopædia Britannica, Ninth Edition, v. 12.djvu/581

565 HYDROZOA 565 Zool., vols. xv., xix., and Jenaische Zeitsch., vol. via., 1874). Relationship of the Ctenophora to the Hydrozoa. The remarkable medusa-form recently described by Haeckel (Sitzungsber. Jenaische Gesellsch., 1878) as Ctenaria cteno- phora, and classed by him amongst the Anthomedusce, seems to furnish a very direct transition from the structure of a medusa to that of such a ctenophor as Cydippe (Pleuro- Fm 57. Floating colonies of Siphonophora. A, Diphyet campanulata. li, A group of appendages from the stem of the same Diphyes. C, Physophora hydrostatica. D, Separate nectocalyx of the same. , Cluster of female sporosacs (aborted medusae) of Agalma tarsii. a, stem or axis of the colony; a, pneumatocyst (air-bladder); m, nectocalyx; c, sub-umbrellar cavity of nectocalyx; t&amp;gt;, radiating canals of the umbrella of the nectocalyx: o, orifice formed by the margin of the umbrella ; t, hydrophyllia in Ji, dactylozooids in C; n, stomach; t, tentacles; g, sporosacs. (From Gegenbaur.) brachia). The woodcut and appended explanation (fig. 58) copied from Haeckel s memoir will render the relations of the two forms clear. Ctenaria has the margin of its disc narrowed so as to give the organism a spherical form. The approximated margins bound an orifice leading to the sub-umbrella space. This orifice corresponds to the so- called mouth of a Cydippe. Further, Ctenaria has two, and only two, long-fringed tentacles, like those of Cydippe, and each springing from a pocket as in that genus, and on the surface of its spheroidal umbrella eight rows of differentiated ectodermal cells, which though not ciliated FIG. 58. Ctenaria Clcnophora (Ilaeckcl), one of the Anthomedmce, connecting that group with the Ctenophora. A, lateral view of the entire medusa ; R, two horizontal views, that to the left representing the surface of the aboral hemi sphere, that to the right a section passing nearly cquatorially. a, the eight (ciliated?) rows of thread-cells, adradial in position, and corresponding to the eight ctenophoral zones of Pleurobrachia; b, jelly of the umbrella; c, circular muscle of the sub-umbrella ; d, longitudinal muscles of the sub-umbrella; e, stomachal dilatation of the enteric cavity ; /, the sixteen oral tentacles ; g, the four perradial generative glands in the stomach wall (manubrium) ; h, tho four perradial primary radiating canals ; &amp;lt;, the eight adradial bifurcations of the preceding; t, ring canal in the margin of the umbrella; 7, velum; m, the two lateral tentacle pouches; n, the two lateral unilaterally fringed tentacles; o, the apical cavity (infundibulum) above the stomach. The canal system, with its four primary and eight secondary rami agrees in Ctenaria and Pleuro brachia. The mouth of the latter is homologous with the margin of the umbrella of the former. The mouth of Ctenaria is homologous with the junction of the so-called funnel of Pleurobrachia with its so-called digestive cavity. This last is the homologue of the sub-umbrellar cavity of Ctenaria. The apical opening or openings of the funnel of Ctenophora is paralleled ,by the stalk canal of medusas, whilst the agreement between the tentacles and their pouches in Ctenaria and Pleurobrachia is complete. correspond closely in position with the eight ctenophoral ambulacra of Cydippe. The disposition of the enteric canal- system of Ctenaria is, as shown in the cut, also transitional in the direction of Cydippe. Apart from the existence of Ctenaria, the homologies suggested by Haeckel between Hydromedusce and Ctenopkora are such as to commend themselves very strongly to acceptance. (E. K. L.) HYDRUNTUM. See OTRANTO. HYERES, a town of France, in the department of Var and arrondissement of Toulon, about 3 miles from the coast of the Mediterranean. It is connected by a branch line with the railway from Toulon to Cannes, and by dili gences with the neighbouring towns. The town proper is situated on the south-eastern side of a steep hill (650 feet high) which forms one of the last buttresses of the Maurettes, a group of picturesque hills covered with olive, pine, and cork trees, and underwood of myrtles and other shrubs. In front, towards the south and south-east, a fertile plain, once famous for its orange groves, and now mainly occupied by vineyards and farms, stretches to the sea, while towards the south-west, across a narrow valley, rises a cluster of low but well-clad hills. The older part of the town, still on its eastern and northern sides sur rounded by its ancient and dilapidated wall, is a labyrinth of steep dirty streets ; but the new quarters which have grown up at the foot of the hill have handsome boulevards and villas, many of them with beautiful gardens full of semi-tropical plants. Of best note among the objects of interest at Hyeres are the house (Rue Rabaton, No. 7) where Massillon was born ; the cathedral or church of St Louis, a low building of the 12th century (restored in 1840), which belonged to the Cordeliers; and the ancient castle, crowning the highest part of the hill. The Place des Palmiers takes its name from the seven palm trees planted there in 1834. On the plain between the town and the sea are large nurseries, an excellent jardin d ao- climatation, and the famed kitchen gardens which supply Paris with early fruits and vegetables and with roses in winter. There are extensive salt-beds on the peninsula of