214 NATURAL HISTORY SOOIETY OF DUBLIN. 
openings between these two portions. The ovaries are in the general 
cavity, and are invested by a delicate membrane, which is continued 
in the form of eight mesenteric slender bands to the body of the tube, 
as is seen in fig. 6. 
In his ‘‘ Icones Histologice,’’ Prof. Kolliker, when treating of the 
hardened connective tissue met within the Alcyonaria, divides the 
denser structures into :-— 
I. Hard structures, which are in substance made up of small isolated 
bodies of a fixed shape (such as the calcareous spicules of Alcyo- 
nide). 
If. Hard structures, forming a more or less compact structure. Of 
these there exist :— 
1. Hard calcareous bodies, either isolated or coalesced together, 
and in combination with a horny or chalky internodal sub- 
stance, or occurring alone as coalesced calcareous substance 
(Axis of Melithzeacese, Sclerogorgiacese, and Coralline). 
2. Lamellated structures, which may be formed as secretions, and 
which, when calcified, leave, after the removal of the salts, an 
organic remainder preserving the same outline. Here be- 
long 
a. The horny axis of Gorgonide and Antipathide, and the horny 
internodes of Isis. 
b. The more or less calcified lamellose axis of Gorgonidee (Prim- 
noa, Plexaurella, Isis, &c.), and Pennatulide. 
3. Crystalline structure, which seems to increase through a deposit 
of chalk from a pre-existing structure, as, after the removal of 
all the salts, there is still left a small, almost inappreciable 
organic residue. Here are placed :— 
a. The greater number of those polyps with merely superficial 
skeletons (Tubipora) ; and 
6. Structures like the chalky skeletons of the Madrepores. 
The structure, however, of the skeleton of Tubipora, as will be seen 
from the above, is certainly not crystalline; and the manner in which 
it is deposited differs in no essential particular from that described in 
section IJ. 1. Fusiform spicules are secreted by the ectodermic layer ; 
these spicules around the base of the tentacles are of a white colour, and 
in many cases are simply fusiform, not warty; but those at a little dis- 
tance from the base of the tentacles not only assume a light-red colour, 
but become crowded over with warty excrescences, and there is ne 
to be found a gradual growing together and consolidation of those 
around the edge of the tube—that is, where this is formed. In the case 
of a young bud, there is at first no tube, the spicules having not yet 
become coalesced ; they are here simply placed side by side. 
