550 ZOOPHYTA. SERTULARIADvE. Valkeria. 



are slightly attenuated. The body of the polype is distinctly visible through 

 the transparent covering. In the branches it is somewhat dusky, but be- 

 comes paler towards the cells. The foot-stalk of the polype, which corres- 

 ponds with the foot-stalk of the cell, is narrow, but it suddenly enlarges in 

 the cell to form the body, nearly of the same shape with its covering, at 

 the summit of which the tentacula are disposed in a a circle ; these are about 

 20 in number, linear, blunt at the extremity, and divided into about 10 

 rough raised joints. Above the circle of tentacula there is a globular head, 

 containing the mouth. The polypes are not verv irritable ; for, even when 

 pricked with a needle, they seldom retreat completely within their covering, 

 and when left at rest, soon expand themselves, the summit of the body be- 

 coming even with the margin of the cell, and the tentacula diverging or fold- 

 ing backwards on its external surface. When in an active state, I have ob- 

 served the water taken in at the mouth descend, for the space of several se- 

 conds, through the gelatinous parenchyma of the body and foot-stalk, and 

 again return to be ejected. The fluid thus circulating, did not seem to move 

 in a solid body through tubular vessels, but to be divided into minute glo- 

 bules, which permeated a cellular structure — This species is vivacious, the 

 polypes bearing to be kept out of the Avater for more than a day without pe- 

 rishing. It is, indeed, a littoral species, living in places left dry every tide. 

 When kept in water, without being changed, the polypes soon contract with- 

 in the cells, and the body of the polype ceases to be visible in the stems. In 

 some specimens, which I had neglected for upwards of a fortnight, the water 

 not having been renewed during that time, I found all the polypes in the 

 cells shrivelled up, and numerous white threads projecting from the branches. 

 Upon examining the origin of these threads, I found that some of them pro- 

 ceeded from the base of the stems, but in general they were formed from an 

 elongation of the foot-stalk of the denticle, its cup having disappeared. The 

 filaments consisted, as in the stalks from which they proceeded, of a soft co- 

 vering, and a contained medullary cord. The extremities of these filaments 

 were club-shaped ; and soon assumiug the form of a cell, gave opening to the 

 tentaculaof a polype which had been formed within. The base of this new 

 cell was annulated, as in the older ones. 



195. C. verttcillata. — Stem erect, slightly branched; cells 

 campanulate, with denticulated margins, supported on long 

 twisted foot-stalks, arising in 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 several inches, stem of straight tubes, each tube giving out cells 



;it equal distances with the other; the foot-stalks are narrow, the cells large 



and wide. 



Gen. LXX. VALKERIA. — Cells ovate, with a narrow 

 base ; polypi with 8 regularly ciliated tentacula ; stems de- 

 licate. — This genus is dedicated to the late Dr Walker, 

 Professor of Natural History in the University of Edin- 

 burgh, a laborious and an accomplished naturalist. 



196. W.cuscuta. — Stem with subverticiUate branches; cells 

 usually in pairs, opposite. 



Climbing Dodder-like Coralline, Ellis, Cor. 28. t. xiv. f. 26. c — Sertula- 



