TUBIPOKA. 



71 



(155.) The Tubipora musica (fig. 32, a) is the species which has been 

 most carefully studied ; and the details connected with its organization 

 will be found of the highest importance, as affording a clue to the in- 

 vestigation of other forms, to be mentioned hereafter. The Tubiporae 

 live in society, but do not appear to be organically united as the com- 

 pound polyps are. A group of these animals presents several stages of 

 tubes, placed one above another (fig. 32, a) : the tubes are generally 

 straight, and nearly parallel to each other, but appear slightly to di- 

 verge as radiating from a common centre ; they are separated by con- 

 siderable intervals, and reciprocally support each other by horizontal 

 laminae of the same substance as the tubes themselves, which unite 



Tubipora musica. a, a portion exhibiting several stages of tubes ; 

 b, an isolated tube ; c, polyp expanded. 



them. From each tube a polyp is protruded, of a brilliant grass-green 

 colour, sometimes of a lilac or rose tint, the mouth being surrounded by 

 eight tentacles, which are furnished along their edges with two or three 

 rows of minute fleshy papillae. 



(156.) The visceral cavity is long, tubular, and contains eight fleshy 

 lamellae (fig. 33, 1, e). These lamellae aid, by their muscles, both in the 

 contraction and expansion of the polyp. The stomach is very short 

 compared with the whole length of the visceral cavity, and, as in the 

 Alcyonium figured above, is connected with the sides of the cavity by 

 the visceral lamellae. 



Six of these lamellae, in a specimen examined by Dana, were sper- 

 matic, being bordered below by a white convoluted cord, while the other 

 two gave origin to large clusters of milk-white ovules, which occupied 

 nearly the whole diameter of the cavity. These ovules were of various 

 sizes, and spherical in shape, or nearly so. Some observers have found 



