ORDER ACTINOIDEA. 45 
clusters are attached in a corresponding manner to the margin of the 
ovarian lamelle. The ovules, though sometimes retained in the cavity 
till they are developed, generally pass out before, and, in either case, 
escape takes place through the stomach and mouth. 
The similarity between these animals and the Hydroidea is hence 
very close. The localisation of the genital functions in distinct organs 
appears to be the character upon which their principal differences 
depend. The relation of the visceral cavity of these animals to the 
tubular axis of the Sertularia is obvious. Though extremely short in 
the Actinia, we find it several times longer than the stomach in the 
Zoanthide, and still longer, and taking the form of a slender tube, in 
the Tubipore and Alcyonia. 
Subdivision of the Actinoidea. 
39. The facts considered lead to a natural subdivision of the group 
Actinoidea. In the Actinia and Palythoa the tentacles are numerous 
and naked, and have a puncture at apex, while, in the Tubipora 
and allied species, these organs are but eight in number, and are 
fringed with papille, each with its minute puncture, and none at the 
extremity of the tentacle. The Actinoidea are hence naturally subdi- 
vided into the two following groups: 
I. Acrinarta.— Tentacles, (mith few exceptions,) naked or not papil- 
lose, siz, twelve, or more in number. This division includes the Actinias, 
Madrepores, Astras, &c. (The cells in the coral-making species are 
more or less perfectly radiate within.) 
II. Atcyonaria. Tentacles fringed mith papille, eight in number. 
This division includes the Tubipores, Gorgonias, Alcyonia, &c. 
(The cells of the coral-making species are never radiate or striate 
within. )* 
* The fact that in a compound Alcyonium the tubular visceral cavities of the several 
polyps branch from one another, with a free intercommunication, has been considered as 
widely separating the Aleyonaria from the Actinaria. In the Tubipore among the former, 
however, this connexion is not more perfect than in the Zoanthide, and the same is true 
of the young state of the polyp-bud in many species. The seriate polyps in a Meandrina 
have even a more open communication, and in some of the compound Fungide adjacent 
polyps have scarcely any thing but a mouth that can be said to be private property. The 
peculiar character of this connexion between polyps in certain Alcyonaria merits notice, 
but not the importance which has been attached to it, 
12 
