Boone, Coelenterata, Cy^uises of "Ara" and "Alva" 73 



grains of coral sand agglutinated by the slimy secretions of the 

 polyp; as the animal grows these grains become embedded and 

 form a calcareous body- wall from extraneous origin, reinforcing 

 the organism. 



The tentacles are externally devoid of papillae and are each a 

 hollow tube with a minute apical aperture. Internally they com- 

 municate with the visceral cavity by a duct beneath the radial 

 lines of the disk. The mouth is a single aperture in the center of 

 the disk, without appendages, and opens into the stomach, which 

 occupies the upper fourth of the interior and is connected with the 

 visceral cavity by a series of fleshy laminae. 



The visceral cavity which is cylindrical, extends to the base 

 of the polyp-mass. This stomach has a muscular arrangement 

 enabling it to close at the bottom. The spermatic cords border the 

 lamellae and extend from below the stomach nearly to the bottom 

 of the cavity, each cord being very convoluted and possessing 

 vibratile cilia. Besides the spermatic cords there is attached to 

 the margin of each primary lamella, just below the stomach, a 

 pair of flat, branchia-like organs ; these are transparent and under 

 high magnification are shown to possess vibratile cilia. 



References: Alcyonium papillosum, Pallas, P. S., Elenchus 

 Zoophytorum Hay. Apud. Petrum van Cleef , 1766, p. 350. 



Alcyonium tuberculosum, Esper, E. J. C, Die Pflanzenthiere in 

 Abbidungen nach der Natur, etc., Nurnberg, 1791, Alcyon. 

 II Thl. Forts., p. 68, taf. 23, figs. 1-2 



Palythoa fiavoviridis, Ehrenberg, C. G., Corallenthiere des 

 Rothen Meeres, p. 47, 1834, Kgl. Akad. Wissensch, Berlin, 

 1834, p. 47; Dana, J. D., U. S. Explor. Exped. Zoophytes, 

 vol. VII, 1846, p. 426. 



Palythoa argus, Ehrenberg, C. G., loc. cit., p. 48. — Dana, J. D., 

 loc. cit., p. 427. — Milne Edwards, H., et Haime, J., Recher- 

 ches et classif . des Polypiers recents et f ossiles, Paris, 1848-49, 

 Coral, t. I, p. 305. — Klunzinger, C. B., Korallthiere des 

 Rothen Meeres, Th. I, Alcy. u. Malacod. 1877, (Berlin) , p. 66, 

 taf. 4, fig. 7. 



