Rain is very scarce, but the canals supply ample water for cultivation and all other purposes.
Numerous canals intersect the district, affording ample means of irrigation.
Alkmaar is a typical North Holland town, with tree-lined canals and brightly coloured 17th-century houses.
Canals lead from Milan to the Ticino, Adda and P0.
In this order the radial canals are represented only by wide gastric pouches, and in the family Solmaridae are suppressed altogether, so that the tentacles and the festoons of the ring-canal arise directly from the stomach.
Canals from Chau-Doc to Ha-Tien and from Long Xuyen to Rach-Gia join the Mekong with the Gulf of Siam.
Of these canals the best known, and probably the greatest, was the Nahrawan, which, leaving the Tigris, on its eastern side, above Samarra, over loo m.
On the west side, however, there are the remains of several canals or channels, some still carrying water, one of which, the Shattel-Hai, leaving the Tigris at Kut-el-Amara, and emptying into the Euphrates at Nasrieh, is still navigable.
The radial canals may be simple or branched, primarily four, rarely six in number.
We can distinguish (I) digestive endoderm, in the stomach, often with special glandular elements; (2) circu-, latory endoderm, in the radial and ring canals; (3) supporting endoderm in the axes of the tentacles and in the endodermlamella; the latter is primitively a double layer of cells, produced by concrescence OC-- = w.?"
40); in Geryonia, however, it remains double, and the centripetal canals arise by parting of the two layers; (4) excretory endoderm, lining pores at the margin of the umbrella, occurring in certain Leptomedusae as socalled " marginal tubercles," opening, on the one hand, into the ring-canal and, on the other hand, to the exterior by " marginal funnels," which debouch into the sub-umbral cavity above the velum.
Buds may be produced from the manubrium, radial canals, ring-canal, or tentaclebases, or from an aboral stolon (Narcomedusae).
Hence the gonads are found on the manubrium in Anthomedusae generally; on the base of the manubrium, or under the gastral pouches, or in both these situations (Octorchidae), or under the radial canals, in Trachomedusae; under the gastral pouches or radial canals, in Narcomedusae.
- Trophosome only known in one genus (Thaumantias), similar to that of the Eucopidae; gonosome, free medusae with otocysts inconspicuous or absent, with usually four, sometimes eight, rarely more than eight, radial canals, simple and unbranched, along which the gonads are developed, with numerous tentacles bearing ocelli and with marginal sense-clubs.
Eight radial canals, eight gonads, stomach not prolonged into manubrium; tentaculocysts enclosed.
Eight radial canals, two, four or eight gonads; tentacles numerous; tentaculocysts free; stomach prolonged into manubrium.
Four or six radial canals; gonads band-like; stomach prolonged into a manubrium of great length; tentaculocysts enclosed.
Similarly the ring-canal runs round the edge of the lobe as the so-called festoon-canal, and then runs upwards under the peronium to the base of the tentacle as one of a pair of peronial canals, the limbs of the V-like figure already mentioned.
NORFOLK, a city and port of entry of Norfolk county, Virginia, U.S.A., on the northern side of the Elizabeth river (an arm of the Chesapeake Bay) and at the mouth of its eastern branch, and on the Albemarle and Chesapeake and the Dismal Swamp canals, about 90 m.
None of these canals is serviceable at the present time, and few carry water in any part of their course, even in flood time.
At the point of entering the alluvial plain the bed of the Tigris seems to be lower than that of the Euphrates, so that the canals run from the latter to the former stream.
The canal and river system attains its greatest utility in the north, northeast and north-centre of the country; traffic is thickest along the Seine below Paris; along the rivers and small canals of the rich departments of Nord and Pas-de-Calais and along the Oise and the canal of St Quentin whereby they communicate with Paris; along the canal from the Marne to the Rhine and the succession of waterways which unite it with the Oise; along the Canal de lEst (departments of Meuse and Ardennes); and along the waterways uniting Paris with the Sane at Chalon (Seine, Canal du Loing, Canal de Briare, Lateral canal of the Loire and Canal du Centre) and along the Sane between Chalon and Lyons.
It assigns its quota of taxes (contingent) to each arrondissement, authorizes the sale, purchase or exchange of departmental property, superintends the management thereof, authorizes the construction of new roads, railways or canals, and advises on matters of local interest.
The term sailor is used in a very wide sense and includes all persons earning their living by navigation on the sea, or in the harbours or roadsteads, or on salt lakes or canals within the maritime domain of the state, or on rivers and canals as far as the tide goes up or sea-going ships can pass.
Water traffic on the Euphrates and canals was early very considerable.
Navigable canals had in 1886 a total length of abput 655 m.; they are principally situated in Piedmont, Lombardy and Venetia, and are thus practically confined to the P0 basin.
The P0 is itself navigable from Turin downwards, but through its delta it is so sandy that canals are preferred, the P0 di Volano ~.nd the P0 di Primaro on the right, and the Canale Bianco on the left.
The great extension of Italian coast-line is thought by some to be not really a source of strength to the Italian mercantile marine, as few of the ports have a large enough hinterland to provide them with traffic, and in this hinterland (except in the basin of the Po) there are no canals or navigable rivers.
In Willia, Geryonia, &c., however, the tentacles and radial canals are on the plan of six instead of four (figs.
The stomach may be altogether lodged in the manubrium, from which the radial canals then take origin directly as in Geryonia (Trachomedusae); it may be with or without gastric pouches.
The medial portion forms radiating tracts of fibres, the so-called " bell-muscles " running underneath, and parallel to, the radial canals; when greatly developed, as in Tiaridae, they form ridges, so-called mesenteries, projecting into the sub-umbral cavity.
The next step is illustrated by the female gonophores of Cladocoryne, where the radial and ring-canals F G H Modified from Weismann, Entstehung der Sexualzellen bei den Hydromedusen.
In some Leptomedusae the gonads are formed on the radial canals and form protruding masses resembling sporosacs superficially, but not in structure.
As medusae are known to bud medusae from the radial canals there is nothing impossible in Aliman's theory, but it cannot be said to have; received satisfactory proof.
- Tropho- some unknown; gonosome, free medusae, with deep, bell-shaped umbrella, with interradial gonads on the base of the stomach, with branched radial canals, and correspondingly numerous hollow tentacles.
Trophosome (only known in one genus), polyps with two tentacles forming a creeping colony; gonosome, free medusae with four, six or more radial canals, giving off one or more lateral branches which run to the margin of the umbrella, with the stomach produced into four, six or more lobes, upon which the gonads are developed; the mouth with four lips or with a folded margin; the tentacles simple, arranged evenly round the margin of the umbrella.
- Trophosome only known in one genus (Polycanna), and similar to the preceding; gonosome, free medusae with otocysts and with at least eight radial canals, often a hundred or more, simple or branched.
- Trophosome unknown; gonosome, free medusae, with four or six radial canals, bearing the gonads, with numerous tentacles, between which occur sense-clubs, without otocysts.
- Trophosome unknown; gonosome, free medusae of deep form, with radial canals branched in a feathery manner, and After Haeckel, System der Medusen, by permission of Gustav Fischer.
(From Moseley.) irregular coenosarcal canals, the coenosteum may contain, in its superficial portion, chambers or ampullae, in which the reproductive zoids (medusae or gonophores) are budded from the coenosarc.
The gonads are on the radial canals or on the stomach (Ptychogastridae), and each gonad may be divided into two by a longitudinal sub-umbral muscle-tract.
- Four radial canals, four gonads; stomach not prolonged into the manubrium, which is relatively short; tentaculocysts free.
Olindiadae, with four radial canals and four gonads; manubrium short; ring-canals giving off blind centripetal canals; tentaculocysts enclosed.
Eight very broad radial canals; ex-umbrella often provided with lateral outgrowths; tentacles differing in size, but in a single row.
It is also known as the Ko-kayaing, so called from the original nine canals of the district.
He is alleged to have completed the system of nine canals and weirs in three years' time.
In length, of which canals cover 3031 m., are also classed under la grande voirie; they are the property of the state, and for the most part are free of tolls.
And Kinda canals by means of the navigable Starlet.
The waters of the two rivers have, however, been made to communicate by artificial cuts and canals in more than one place.
Besides the wider vertical pore-canals and the narrower, FIG.