44 ZOOPHYTES. 



noidea.* We have nothing to add on the processes of digestion and 

 circulation in these animals, in addition to what has been already 

 presented, in our remarks on the Actinia and Palythoa. Nothing 

 like branchiae were observed in the Tubipore examined. 



General characteristics of the animals above described. 



38. The species described in the preceding pages, have been 

 selected from the most widely-separated groups among the Acti- 

 noidea, and are types of important divisions. The points of agree- 

 ment constitute the characteristics of this order, and may be here 

 enumerated. 



1. The Actinoid polyp contains a large cul-de-sac visceral cavity, 

 divided radiately into compartments by fleshy lamellae, and a stomach 

 suspended in it beneath the centre of the disk. Several lamellae 

 are united by their inner margins to the stomach, and aid, by their 

 muscular action, in the expansion of the stomach and the expansion 

 and contraction of the whole animal. 



2. The stomach communicates below with the visceral cavity, 

 through an opening which may be closed by muscles. Its walls are 

 muscular, and the organ admits of great dilatation, or may be con- 

 tracted, at the will of the animal, to a slender tube. 



3. Digestion takes place in the stomach; and thence, after exclud- 

 ing the refuse matter by the mouth, the results of digestion pass into 

 the visceral cavity, to be aerated and elaborated through the air in 

 both the external and the admitted waters, at the same time that these 

 fluids are distributed, by an imperfect circulation, throughout the 

 animal, and assimilated wherever needed for changes in progress. It 

 is probable that excretions take place through the sides of the polyp, 

 and by the waters which the animal ejects elsewhere on contraction. 



4. Reproductive functions reside in the visceral lamellae, part of 

 which are spermatic and part ovarian. All of these lamellae are thus 

 genital, excepting probably the upper portions of the larger lamellae, 

 which are attached to the stomach, and in this part are muscular. 

 The testes or spermatic organs have the form of white convoluted 

 cords, and are attached to the margin of the lamellae. The ovarian 



* This has been observed in certain species of the tribe, by Professor Grant and Milne 

 Edwards. — For an interesting account of the developement of the ova, see a paper by Dr. 

 Grant, in Jameson's Edinburgh New Philosophical Journal, vol. i. p. 152 ; and also on 

 the general structure and reproduction of the Alcyonida, a memoir by Milne Edwards, in 

 the Annates des Sci. Nat., 2d ser., iv. (1835), p. 321. 



