306 Proceedings of Royal Society of Edinburgh. [sess. 
process is continued for a considerable time, there being no dearth 
or vacuity in the ovary. Mr Gardiner finds, however, that in 
a specimen 40 mm. long some of the mesenteries bear no ova, 
but on most of them isolated ova are present. On none of the 
mesenteries are there any small ova to take the place of those 
which had escaped or were about to escape. “It seemed obvious 
that a critical period had been reached, after which ova ceased 
to develop. . . . There is no direct proof — indeed it is only a 
presumption — that the polyp now dies.” This seems, however, 
very probable, for the largest specimen among over 600 
from the Cape of Good Hope measured 42 mm. in length, and 
Mr Gardiner dredged eight dead ones in the Maldives which 
average about 38 mm. His largest living specimen, the one 
described above, measured 40 mm. 
Mr Gardiner has been good enough to re-examine his material, 
and to give us some valuable information respecting the number 
of growth-lines on these old specimens. These growth-lines are 
difficult to count in specimens in which the calicle is longer than 
20 mm. He found that the maximum number of lines, allowing 
for the cut-off base, is about 24 in the largest specimens. We 
may assume, therefore, that these specimens of Flabellum , 
which were obviously nearing the end of their reproductive 
powers, and probably also near the end of life, were about 
twenty-four years old. 
Mr Gardiner states (1902, p. 469) that he examined, on the 
reefs of Rotuma, a large area covered by Madrepora pulcra, Brook, 
var. alveolata, Brook, and found that most of the polyps were dead. 
The living polyps were all female, and the reproductive organs 
were in the condition described above for the 40 mm. Flabellum , 
that is, the ova were either few and isolated, or had been 
already discharged. In this and in other similar cases mentioned 
there were no external conditions, such as silting up, which might 
account for death. Each colony has presumably originated from 
single ovum, and the limitations in the size of the colonies point 
to some reason innate in the organisms themselves. “There can 
be no rejuvenescence, and the operative cause is probably the 
same as that which ultimately produces the death of our forest 
trees,” but Mr Gardiner does not consider that he is able to offer an 
