108 
MR. H. N. MOSELEY ON THE 
but I am uncertain about this point, it being very difficult to get a view of all the 
filaments uninjured in any one polyp. To which sides of the mesenterial plates the 
filaments are attached I have not made out. 
Out of at least a hundred polyps examined from the colony of Heliopora hardened 
for examination, only three were found to contain generative organs ; in each of the 
cases ova. In two of the polyps a single ovum only was present, in the third four 
ova attached singly to four mesenteries. The ova are attached to the edges of the 
muscular margins of the mesenteries at a point about halfway between the origin and 
insertion of the fibres composing the lower border of the muscle (Plate 8. fig. 1). 
The ovum is attached to this border by a specially developed mass of entodermic cells, 
and at its point of attachment is in close relation with the mesenterial filament. The 
ova, as shown (Plate 9. fig. 14), are large, measuring -21 millim. in diameter (the 
smallest observed measured T7 millim. in diameter) ; they are composed of an outer 
membranous capsule, by means of which they are attached in position, containing a 
mass of yelk-globules, in which lies a germinal vesicle and germinal spot. 
It was not determined which of the mesenteries bore ova, or whether those with long- 
filaments bore them or not, the expectation that abundance of fertile polyps would be 
found for examination having been disappointed. In Plate 8. fig. 1 the mesenterial 
filament is, in the drawing, stopped short above the ovum in order to allow it to be seen. 
The filaments belonging to the septa bearing ova hang down below the ova. No trace 
of any male elements was found in any polyp. The colonies of Heliopora are probably 
unisexual. 
The investigation of the positions of the dorsal and ventral aspects of the polyps in 
the Heliopora colony relatively to the axes of growth is extremely difficult, because 
when a horizontal section is cut sufficiently deep down to display the muscular arrange- 
ment, nothing remains to hold the various sections of polyps in position but the imbedding 
substance made use of ; and where the only substance at command, as in the present 
case, is wax, the sections with the wax unremoved are almost too opaque and indistinct 
for observation. By examining such sections, held together by the wax and made 
transparent with glycerine, I have found that the polyps (although they are often 
turned on their central axes to a considerable extent, so that the long axes of their 
stomachs are not by any means parallel, but often inclined to one another at very 
considerable angles) have nevertheless their dorsal surfaces or the intermesenterial 
spaces devoid of retractor muscles (“ Dorsalfacher ”) always nearer to the summits of the 
colony than are the “ Ventralfacher.” The “ Dorsalfacher” thus show a general tendency 
to take a superior position, i. e. lie uppermost, in the vertical plates of which the 
colony is composed. The entire coral makes up a fiat plate, with two outer surfaces, 
towards which the polyp-tubes are directed in curves on either hand from the vertical 
axis of growth ; and the polyps thus curving away from one another have their 
“ Dorsalfacher” approximated or are placed back to back. 
