THE ANATOMY OF THE HADREPORAEIA. 425 



though obviously present, are uot sufficiently developed to 

 admit of a distinction of the mesenteries into pairs. The con- 

 tinuity of the mesenteries radiating outwards from the polyp 

 is constantly broken by synapticulas, The whole of the surface 

 of the colony is practically composed of these radiating slips of 

 mesentery lying between radiating septa, and interrupted by 

 synapticulse ; and, except in the immediate neighbourhood of a 

 polyp, it is often impossible to decide to which individual a 

 mesentery is referable, since neither their direction nor mus- 

 culature afford a clue. Contrary to what one might expect 

 (cf. the more or less comparable condition in Fungia; Bourne, 

 ' Quart. Journ. Micro. Sci.,' xxvii, pi. xxv, fig. 13), even such 

 slips of mesentery as are at no point in contact with the 

 stomatodaeum often exhibit a filamentar (craspedal) thickening. 

 Even at the uppermost ends of the branches, at a distance of 

 perhaps a third of an inch from the nearest polyp, the same 

 arrangement of mesenteries between septa (septo-costae) is 

 found. On these mesenteries the body wall is supported, 

 although in places it appears to rest also on echinulations of 

 the septa ; as will be seen from the figure, there is practically 

 no coenenchyme. Through the inner parts of the colony 

 ramifies a system of canals by which the various polyps are in 

 communication with each other. 



This genus appears to exhibit a distinct degeneration, 

 implied by the low development of the mesenterial filament (a 

 slight lengthening of the ordinary endoderm), and an indi- 

 viduality hardly more marked than in a Poriferan colony. 



A figure and description of the corallum may be found in 

 Verrill, ' Trans. Connect. Acad./ i, p. 545, pi. ix, fig. 4. 



PoCILLOPORA NOBILIS. 



For material of this species I am again indebted to Pro- 

 fesssor Moseley, who obtained it during the voyage of the 

 " Challenger." 



The anatomy agrees almost entirely with that of P. 

 brevicornis, recently described (" Anat. Madr.," iii). The 



