ANATOMY OF MUSSA AND EUPHYLLIA. 27 



the mesoglcea. They are of large size, measuring as much as 

 •Oil mm. across. They are only to be found on a few, and 

 those invariably the shorter mesenteries ; but they were not 

 constant on these, and I am unable to say whether the shorter 

 mesenteries alone are reproductive. As I found no traces of 

 spermatozoa in the specimens which I examined it may be 

 concluded that Mussa is monoecious. 



Euphyllia. — The specimens of this genus were kindly 

 supplied to me by Prof. Moseley, and form a part of the reef 

 corals collected by H.M.S. "Challenger." The corallum is 

 described by Quelch in the ' Challenger Reports/ vol. xvi, p. 

 74, as Euphyllia glabrescens. The description of the 

 species by Milne-Edwards and Haime is as follows: — "Corallites 

 sometimes unite in small series of three or four, but ordinarily 

 separating early. Theca covered with closely set and extremely 

 fine grains. Costse thin, rising slightly near the edges of the 

 calicle, and subcristiform. Calices with irregular boundaries, 

 narrow, and very deep fossa. Septa very irregularly arranged 

 in orders, scarcely exsert, very thin, moderately close together, 

 their faces very finely granular, and presenting parallel striae. 

 Greatest width of the calices 2 centimetres; the diameter of 

 the corallites is somewhat smaller beneath the calices." 



Quelch arranges the septa in five orders, but I found their 

 number very inconstant, and could not make out more than 

 three definite cycles, which are, however, arranged with con- 

 siderable regularity. The septa of the first order are large, 

 and reach in the deeper parts of their courses nearly to the 

 centre of the calyx. Those of the second order are rather 

 shorter, and alternate with those of the first, whilst the septa of 

 the third order are very short and are only to be found in the 

 upper part of the calyx ; they occur in every loculus between a 

 septum of the first and a septum of the second order. A 

 transverse section across part of the calyx, including septa of 

 all three orders, is given in fig. 7. The calcareous tissues are 

 seen to be much thinner and more fragile than in Mussa, and 

 the concentric lines of growth seen in the latter form are not 

 present. The centres of calcification are present as con- 



