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 layers of fibres, so that 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 flesh, 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 Alcyonium. The skin is 
coriaceous, strengthened with calcareous particles, but the in- 
terior offers 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 — 79. 
