History of British animals - University of Guam Marine Laboratory

550 ZOOPHYTA. SERTULARIADvE. Valkeria.are slightlyattenuated. The body of the polype is distinctly visible throughthe transparent covering. In the branches it is somewhat dusky, but becomespaler towards the cells. The foot-stalk of the polype, which correspondswith the foot-stalk of the cell, is narrow, but it suddenly enlarges inthe cell to form the body, nearly of the same shape with its covering, atthe summit of which the tentacula are disposed in a a circle ; these are about20 in number, linear, blunt at the extremity, and divided into about 10rough raised joints. Above the circle of tentacula there is a globular head,containing the mouth. The polypes are not verv irritable ; for, even whenpricked with a needle, they seldom retreat completely within their covering,and when left at rest, soon expand themselves, the summit of the body becomingeven with the margin of the cell, and the tentacula diverging or foldingbackwards on its external surface. When in an active state, I have observedthe water taken in at the mouth descend, for the space of several seconds,through the gelatinous parenchyma of the body and foot-stalk, andagain return to be ejected.The fluid thus circulating, did not seem to movein a solid body through tubular vessels, but to be divided into minute globules,which permeated a cellular structure—This species is vivacious, thepolypes bearing to be kept out of the Avater for more than a day without perishing.It is, indeed, a littoral species, living in places left dry everyWhen tide.kept in water, without being changed, the polypes soon contract withinthe cells, and the body of the polype ceases to be visible in the stems. Insome specimens, which I had neglected for upwards of a fortnight, the waternot having been renewed during that time, I found all the polypes in thecells shrivelled up, and numerous white threads projecting from the branches.Upon examining the origin of these threads, I found that some of them proceededfrom the base of the stems, but in general they were formed from anelongation of the foot-stalk of the denticle, its cup having disappeared. Thefilaments consisted, as in the stalks from which they proceeded, of a soft covering,and a contained medullary cord. The extremities of these filamentswere club-shaped ;and soon assumiug the form of a cell, gave opening to thetentaculaof a polype which had been formed within. The base of this newcell was annulated, as in the older ones.195. C. verttcillata.— Stem erect, slightly branched; cellscampanulate, with denticulated margins, supported on longtwisted foot-stalks, arisingin whorls from the stem.Horse-tail Coralline, Ellis, Cor. 23. t. xiii. f. 20. A—Sertularia ver.Linn. Syst.ii. 1310. Pall. El. 115.— Camp. vert. Lamarck, Hist. ii.113.— Clytia vert. Lamour. Cor. Flex. 202. — Coast of Cumberland,Dr Brownrig, rare.Height severalinches, stem of straight tubes, each tube giving out cells;itequal distances with the other; the foot-stalks are narrow, the cells largeand wide.Gen. LXX. VALKERIA.— Cells ovate,with a narrowbase ;polypi with 8 regularly ciliated tentacula ; stems delicate.—This genusis dedicated to the late Dr Walker,Professor of Natural Historyin the University of Edinburgh,a laborious and an accomplished naturalist.196. W.cuscuta.— Stem with subverticiUate branches; cellsusually in pairs, opposite.Climbing Dodder-like Coralline, Ellis, Cor. 28. t. xiv. f. 26. c— Sertula-