ZOOPHYTA ASTEROIDA. 169 



the Gorgonia is not continued, as in the tree, from the trunk 

 through the branches, but is interrupted at their origins by se- 

 veral intervening hxyers of fibres, so tliat they are rather, as it 

 were, inserted upon the stem than propagations of it ; the axis 

 possesses none of that curious complexity of structure, — of fibres, 

 of sap and air vessels and utricular cells, — which renders the wood 

 so beautiful an object under the microscope ; and lastly there 

 is between the bark and the crust of the zoophyte nothing but 

 contrasts and discrepancies.* 



The axis of a Gorgonia, at least of our native species, resem- 

 bles a tree in this, that the stem always bears a certain propor- 

 tion in thickness to the size of the polypidom, being slender in 

 the small, and thicker in the larger specimens : it tapers from 

 the rock or dilated base, and becoming gradually more gracile 

 and attenuated, disappears at the extreme points of the branch- 

 es. It is covered throughout with the fleshy which is the same 

 in structure at all points, but thicker and more loaded with po- 

 lypes towards the ends of the branches than on the stem or 

 near their base, whence the former generally assume a cylindri- 

 cal form. This flesh when dry is earthy and friable, a consi- 

 derable proportion of carbonate of lime entering into its compo- 

 sition ; but in a recent state it is soft and fleshy, and excavated 

 with numerous cells for the lodgement of the polypes. When 

 a portion of a branch is macerated in a weak acid, the lime is 

 entirely removed, but the branch retains its original size and 

 figure, and shows the frame-work to be an irregular close tex- 

 ture of corneous fibres, the interstices of which had been pro- 

 bably filled in part with a gelatinous fluid. And this is much 

 the same structure that we find in the Alcvonium. The skin is 

 coriaceous, strengthened with calcareous particles, but the in- 

 terior off"ers a fibrous net-work containing a transparent jelly in 

 the squares, and permeated with a certain number of longitu- 

 dinal cartilaginous tubes. The soft part of Pennatula seems 

 more uniformly fleshy or gelatinous, and its polypes are placed 

 only on certain wings or appendages of the polypidom, but the 

 skin is also coriaceous, and has moreover in its substance a great 

 number of calcareous spicula placed parallel to one another, and 

 which must greatly add to its consistency and strength. 



* Ellis and Soland. Zoophytes, 76 — 70. 



