592 ANATOIMY OF XEOHELIA PORCELLAXA (mOSELEy). 



Moseley omits to mention certain apertures which are present in the peritheca' 

 (= coenenchyma) of a dried Challenger specimen now in the British Museum. These 

 apertures are larger and more numerous in our specimen which appears to be younger, 

 the peritheca is also less diffuse, and the costae more distinct, (compare Moseley, 

 Challenger, PI. X. figs. 7 and 7 a with figs. 1 and 2). 8. The hollow tube com- 

 prising our specimen is lined by a horny membrane which lies in contiguity with 

 the calcareous skeleton with which it conforms in outline and is interrupted in like 

 manner at the apertures (Fig. 1). 



These were the chief points of interest together with an opportunity of ex- 

 amining the soft parts which led me to undertake the investigation of this species, 

 the results of which are now recorded. 



Calcareous skeleton : — 



In his description of the peritheca Moseley says, "The surface of the coenenchym 

 is marked all over by very slightly elevated rounded ridges which traverse it irregu- 

 larly, but with a general longitudinal direction, and are continuous at the margins 

 of the calicles with the costae." These ridges show more clearly in our specimen, 

 than in Moseley's, they are better seen after the soft parts have been removed by 

 immersion in a dilute solution of Caustic Potash followed by brushing gently. The 

 ridges are then seen to be studded with gi-anular protuberances. These however are 

 even better seen in a calcined specimen. 



Septa. There are twenty Septa arranged in three cycles. While the number of 

 the Septa is constant in all the calicles which Moseley and I have examined, in some 

 cases, there is a tendency for them to lose their symmetry of arrangement (see 

 calicle S. Fig. 2). In Lophohelia prolifera (12), also a member of the Oculinidae, 

 there is a greater irregularity in the number and arrangement of the Septa. Fowler 

 remarks of this species that the total number of the Septa probably varies with 

 the age of the individual polyp. 



Peritheca. The apertures in the peritheca are larger and more numerous in our 

 specimen than in Moseley's. In the latter they are so small, that their significance 

 was perhaps overlooked, but Moseley points out that as the colony covers the invested 

 ^objects, the branches of the groiiS'ing coenenchym (peritheca) are soldered together. 

 The apertures referred to above and shown in Fig. 1, are gaps left between the 

 branches as they are soldered together, and probably diminish in size as the colony 

 grows older. 



The Horny Membrane. In Moseley's. specimen which is dried, it is difficult 

 to ascertain if a horny membrane exists between the Gorgonia stem which the colony 

 encrusts and the calcareous skeleton, but as a horny substance of a similar nature 

 to that in our specimen forms a ring round one of tlie apertures, there is reason 

 to believe that the horny membrane is present generally in the genus. 



1 Peritheca— teim originally used by Milue-Edwards and Haime, aud defined by Stanley Gardiner (24), 

 p. 361. 'The Peritheca is that part of the corallum of colonial Madicporaria, which is deposited outside 

 and subsequently to the theca.' 



