516 POLYPI. 



open, either on the summit or sides, to allow the passage of the 

 Polypi. 



Their more simple Polypi appear to be chiefly analogous to the 

 Hydras and Cristatellas. 



TUBIPORA, Lin. 



Simple tubes of a stony substance, each containing a Polypus. These 

 tubes are parallel, and united from space to space by transverse laminae, 

 which has caused them to be compared to the pipes of an organ. The 

 most common species, 



T. musica, L.; is of a beautiful red; its polypi are green, and formed like 

 Hydrse. Very abundant in the archipelago of India. 



TUBULARIA, Lin. 



Simple or branched tubes of a horny substance, from the extremities of 

 which issue the Polypi. 



SERTULARIA, Lin. 



The Sertulariae have a corneous stem, sometimes simple, sometimes ramous, 

 on the sides of which are cells, extremely various in form, that are occu- 

 pied by the Polypi, all connected with a gelatinous stem that traverses the 

 axis, like the medulla of a tree. They increase by ova or buds, which are 

 developed in cells larger than the rest, and of a different form. The vari- 

 ous directions of their cells have caused them to be subdivided. 



FAMILY II. 

 CELLULARIL 



Where each Polypus is adherent in a corneous or calcareous cell 

 with thin parietes, and only communicates with the others by an ex- 

 tremely tenuous external tunic, or by the minute pores which tra- 

 verse the parietes of the cells. These Polypi bear a general re- 

 semblance to the Hydras. 



CELLULARIA, Lin. 



Where these cells are so arranged as to form branching stems in the man- 

 ner of the Sertulariae, but without a tube of communication in the axis. Their 

 substance also is more calcareous. 



FLUSTRA, Lin. 

 We here find a great number of cells united like honey-combs, sometimes 



