ACTINOZOA. 159 



Tiibulosa, the septa are indicated by mere streaks 

 {fig. 36, c). And in the TubiporidcB, a family 

 of Alcyonaria, septa are absent ; each corallite be- 

 ing a simple tube, connected with the thecse around 

 it by horizontal plates, which represent the inner 

 transverse floors of the Tabidata ifig-Z^)- 



Fig. 30. 



TuBipoEA MrsrcA, 

 Fragment of corallum, of the natural size. 



From the Tubiporidce to other Alcyonaria in 

 which the corallum, though sclerodermic, soon 

 ceases to present traces of thecse, a transition, not 

 very abrupt, may be effected. Such intermediate 

 stages, though not of much value to the sys- 

 tematic zoologist, are of great interest in a mor- 

 phological point of view, since the}^ show well the 

 manner in which the complete sclerodermic co- 

 rallum has been formed ; thus at once illustrating 

 its minute structure and the several stages of its 

 development. In Telestlio, the corallum is made 



