50 ZOOPHYTES. 
larger cells, they are nearly equal; while in the latter, half are obso- 
lescent. In the Merulinas, there are seven or eight larger lamelle to 
a fourth of an inch, with three or four intermediate nearly obsolete, 
making in all ten or eleven in this breadth. The same is generally 
true of the Euphyllie and Meandrine. In the Muss, much larger 
species, there are seven or eight to a fourth of an inch, as in the 
Actinia marginata ({ 25), and half of these are quite small or obso- 
lescent. It appears, therefore, that the number varies, in different 
species, from seven to fifteen. The last number is seldom exceeded, 
yet instances of this are found in some Meandrinas and many of the 
attached Fungide. 
II. Ancyonaria. 44. The simple polyps, among the Alcyonaria, 
have a great similarity throughout. The number of tentacles being 
fixed, there is not room for the same diversity of form as in the Acti- 
naria. The principal varieties in external appearance proceed from 
variations in the length and position of the papille#. ‘These appen- 
dages to the tentacles are sometimes quite long, and give a graceful 
delicacy to the flower, scarcely exceeded in the vegetable kingdom.* 
Usually, they form a short fringe in two or three series on either side 
of the rays, as shown in the Tubipora, already described.t In one 
of the species of this genus (T’. syringa), they are so evenly laid 
together that the fringe seems to be wanting. In one of the Xenine, 
found at the Feejee Islands,} the papille are minute wart-like pro- 
minences, scattered over the surface of the ray. Hach little promi- 
nence has the minute puncture at apex, which is characteristic of the 
Alcyonia group. 
IL. SECRETION OF THE CoRALLUM IN THE ACTINOIDEA. 
45. The corallum has been described as in general an internal 
secretion, formed within the polyp, and not a covering enclosing the 
same, asin the Mollusca.) We may examine more particularly the 
mode of its secretion and its relations to the animal. 
There appear to be two kinds of coral secretions among the Acti- 
noidea :— 
1. Secretions formed within the animal which are mostly calcareous. 
* See plate 59, figure 3. + See plate 59, figures 1,2. + See plate 57, figure 2. 
§ This character of these secretions was first pointed out by Ehrenberg, in his Memoir 
on the Corals of the Red Sea, in the Transactions of the Berlin Academy, for 1832. 
Since then, they have been more fully explained by Milne Edwards, in the Annales des 
Sciences Naturelles, for 1838, x., 2d series, 321. 
