178 
ON THE SKELETONS OF ZOOPHYTES. 
is observed to be covered with a series of egg-shaped vesicles, gradually contracted 
towards their inferior part, and arranged with great regularity. Each cell is the 
habitation of a Polyp of a very complex organisation, having the mouth sur¬ 
rounded by 22 tentacula, the margins of each of which are provided with 10Q 
minute vibratile ciliss. It is estimated'"' that in each square inch there are about 
1,800 cells, and ordinary specimens in general contain about ten square inches ; 
so that in this zoophyte there are no less than 18,000 Polypi, armed with 396,000 
tentacula, from the margins of which 39,600,000 ciliae emanate. What an 
enormous complication in so simple a being! 
In the order Corticifera the skeleton is internal, andjthe fleshy crust is moulded 
around the horny or Calcareous axis. The organ of support affords no solid 
protection to the Polypi, there being no cells either upon the stem or branches 
for lodging the same ; these solid parts are marked with longitudinal strise alone, 
to secure the adhesion of the investing fleshy substance, as is easily seen by 
peeling the Calcareous crust from the stem of a Gorgonia , or by inspecting a 
branch of recent Coral. The Gorgonia and Antipathes , so common in all collec¬ 
tions, are examples of Corallidce with an internal horny axis. Although the 
fleshy substance in dried specimens has been dissipated by evaporation, still there 
remains a Calcareous crust which adheres firmly to the horny stem. This crust 
is perforated with numerous small pores, and is coloured in the different species 
with the most lively hues, as yellow, crimson, Vermillion, &c. The Calcareous 
spiculse composing the bark were component parts of the fleshy substance, and 
the delicate tints are due to some peculiar colouring material secreted by the 
organised fleshy portion. These spiculse are analogous to the earthy materials 
embedded in the horny network of 'Porifera , and may probably be destined to 
serve as a compensation for the deficiency of Calcareous matter in the horny stem. 
When we peel off this porous crust, we expose a dark-coloured horny ramified 
frame-work, which is the true skeleton; and by making a transverse section of 
the axis of a Gorgonia , we observe that it is composed of concentric rings, which 
have been successively deposited by the organised gelatinous bark that everywhere 
invests the horny material. The form of the skeleton in this family varies in the 
different genera. From the expanded root a compressed angular or cylindrical 
trunk rises, which divides into numerous branches. These assume a variety of 
forms, being single, double, or anastomosed, straight, pensile, or pinnate in the 
different species. In all the diversity of form, colour, and geographical distribution 
observed in this interesting group, one common character prevails, namely, that 
the internal horny extravascular axis is enveloped in an organised crust, through 
which are scattered Calcareous spiculse, to form the boundaries of cells for lodging 
Grant, Trans. Zoolog. Soc., Yol. I.; Roget’s Bridgwater Treatise , Vol. I. 
