806 



NATURAL HISTORY. 



soft tissue in bands. The lower part of the axis is not covered with zooids, and the upper part may 

 have its surface with zooids on one or both sides in simple series, in spiral series, or in gi'oups on one 

 or both sides. When the upper part of the axis is branched, the pen-shape may be single or double, 

 and crowds of zooids with spinules are arranged on one edge. The ectoderm usually contains cal- 

 careous spiculae. The Sea-pens live in shallow water, and also at great depths, and their distribution 

 in the ocean is very wide. The sub-family Pennatulse contains the genus Pennatula, in which the 

 zooids are on the ventral and lateral sides of the stem, there being always a bilateral arrangement 

 of them on the long cylindrical pinnate stem also. Many are very phosphorescent, and most live in 

 shallow water, some going down to three hundred fathoms. Their colours are often brilliant 

 red, and the specimens may be a foot in length. The stalk, or lower part of the axis, swells out, and 

 then terminates in a slender end, or it may be short and cylindrical. The spicules have the tint of the 

 whole. The zooids are on the tufts, and not on the stem, in the genus Pteroeides. In the genus 

 Virgu laria the root is stout and bent, the axis very long and often curved, and the zooids are on 

 either side, on the short pinnules. Calcareous needles are scanty in the stalk and tentacles. In the 

 genus Scytalium, the zooids, placed side by side, resemble the half of a young leaf, and the pinna? 

 are thick, whilst in Pavonaria, the zooids are on the thick edge of the four-sided stem. A magnificent 



form, called Anthoptilum thomsoni, after the late director 

 of the Challetiger Expedition, has a round and long axis, 

 and the zooids are in many short rows on it. It was 

 found at six hundred fathoms' depth, south of Buenos 

 Ayres, and another species at a depth of 1,200 fathoms. 

 The family Umbellulidse have a long sterile axis, and 

 from about twenty to fifty zooids are grouped together at 

 the upper end, in a more or less umbrella form. Some 

 species were found at a depth of from 1,200 to 2,125 

 fathoms. 



The family Renillidse have a kidney-shaped body, 

 without a solid axis, and the zooids are on one side of 

 their single pinnule. The Veretillida? have an elongate 

 axis, which has retractile zooids over the entire surface, 

 and its lower part is bulbous, naked, or soft. It is divided 

 longitudinally by two intersecting membranes, with a 

 calcareous axis in the lower part of the stem, or it may 

 be simple and fleshy. 



THE FAMILY OF THE GORGONID^E. 

 There are vast numbers of branching, slender-stemmed, 

 compound Alcyonaria living fixed on the floor of the 

 sea at different depths. They have a cellular soft part, in 

 which are the zooids, or polypes, with eight pinnate 

 tentacles, and this surrounds, in the manner of a bark, 

 a more or less horny or calcareous stem, which is fixed 

 at its base. The soft tissue is furnished with sclerites 

 or spiculpe, and a canal system is on the outside of the 

 stem, or sclerobasic axis. It appears to have to do with 

 the general nutrition and symmetrical growth of the 

 whole, and probably it communicates with the visceral 

 cavities of the polypes. The visceral cavities of the 

 polypes are short, and rest, as it were, 011 the outside of 

 the central stem. There are two great divisions of this 



family ; in one the axis is flexible, horny, and only partly calcareous, and in the other it is completely 

 calcareous. The first division relates to the sub-families Gorgonise and Isidinse, and the last to the 

 sub-family Corallinse. 



GROEXLANDicA. 



