8 G. HERBERT FOWLER. 



with free calyces fcf. Cladocora (4), Caryophyllia (6), &c), the 

 polyp is so continued over the lip and outer side of the calyx 

 as to form a covering for its exterior surface to a varying dis- 

 tance (the " Rand-platte" of v. Heider). In Lophohelia this 

 continuation may extend for about 15 mm., or even more ; 

 often it measures much less, and in it the relations of the 

 various body layers are such as have been already described 

 in the forms referred to above; the part of the coelenteron 

 enclosed in this " Rand-platte" is divided up into exoccelic and 

 entoccelic spaces nearly corresponding to those inside the calyx 

 by the peripheral lamellae which were at a former time con- 

 tinuous with the more central mesenteries, but which have 

 been mainly cut off from them by the gradual growth of the 

 theca upwards, though the continuity is maintained above the 

 lip (fig. 6). This explanation, due originally to Dr. von Koch, 

 must undoubtedly apply to this and many other adult 

 forms. 



The general anatomical relations of the polyp, and its agree- 

 ment with forms already described, are shown in the diagram- 

 matic segment of a transverse section (fig. 6) . The " Rand- 

 platte," the mouth disc, tentacles, and stomatodaeum are all in 

 accordance with the normal type. The coelenteron of the living 

 polyp is, as usual, lined by endoderm and mesogloea, apposed 

 directly (except for scattered calicoblasts) to the corallum. 

 At the point, however, where the living polyp ceases, its coelen- 

 teron is separated off from the cavity in the coral which it pre- 

 viously occupied by a plug of decaying (?) tissue, in which no 

 cell-elements or organic structure are recognisable, except occa- 

 sionally the remains of the mesogloea lamina of a mesentery. 

 Into this the living tissues pass gradually. 



The tentacles, which are both ectocoelic and entoccelic, i. e. 

 one over every septum, are knobbed, each knob being such a 

 battery of nematocysts as has been described in Flabellum (2), 

 Stephanotrochus (11), &c. 



The mesenteries which, like the septa, vary in number in 

 different polyps, all bear retractor muscles on their entoccelic 

 faces, i. e. there are no pairs of "directive" mesenteries 



