39^ 



COELENTERATA ANTHOZOA 



standing the difficulty of distinguishing the species, the genus 

 itself is quite well defined. The calices project slightly from the 

 surface of the branches and contain six septa, of which the pair 

 that is parallel with the axis of the branch is the strongest. 

 This strong pair of septa can usually be well seen when a slende: 

 branch of a Madrepore is examined by a lens by transmittei 

 light. At the apex of each branch there is a terminal zooid an 

 in the skeleton an apical calyx. The terminal zooid is (in sonn 

 species at least) different from the lateral or radial zooids. Th 

 former is radially symmetrical and has six long equal digitiforr 

 tentacles, the latter have usually twelve tentacles, of which si 

 are larger than the others. These tentacles alternate, but t' 

 are so arranged on the disc as to give a distinctly bilateral 

 appearance to the zooids. 



The colour of the West Indian Madrepores appears to h 

 entirely due to Zooxanthellae (pp. 86, 125). They are lighter 

 or darker shades of brown, sometimes becoming green, yellow 

 or orange. On the Australian barrier reef and other reefs o 

 the eastern seas the growing points of the branches are variabL 

 and often brilliantly coloured, emerald green, violet, or red 

 giving some of the most wonderful colour effects for which th 

 reef pools are famous. The cause of these brilliant apica 

 colours has not yet been ascertained. 



The genus is found in shallow water of all seas of the tropica 

 belt except on the western side of the continent of America. 



Montipora. In this genus the calices are small and situate* 

 in depressions in the coenosteum, and there are six, sometime! 

 twelve, septa of approximately equal size. There is no termina 

 calyx at the apex of the branches. This is a genus of very variabL 

 form and wide distribution in all tropical seas except on th' 

 shores of the Atlantic Ocean. 



Turbinaria. This genus is usually cup-shaped or foliaceou 

 and twisted in form. The septa may be six to thirty i 

 number. Some of the species of this genus attain to a ver 

 great size in favourable localities. There is a specimen in thi 

 British Museum that is 16 feet in circumference and weighed, 

 when dried, 1500 lbs. 



Fam. 2. Poritidae. The corallum is usually encrusting, 

 foliaceous, lobed or tufted, rarely dendritic. The whole skeleton 

 is built up of a system of trabeculae and stout cross bars, and in 



