Protandry and Senescence in Corals. 
467 
extraneous, environmental causes, the polyp tissues ceasing to 
exercise an efficient, protective influence over the outer parts of 
the epitheca, consequent on its greater thickness. 
With increase of size, beyond 25 mm. in length, the ova ripen. 
Ducts are formed through the thickened nutritive endoderm down 
to the ova, which subsequently escape through them. In sections 
along their lengths they show longitudinal striation, but they are 
very distinctly ducts. They correspond in fact to the structures 
termed “cone nutritif” and “Fadenapparut” in Actiniaria, which 
I would suggest are simply oviducts. 
As the ova ripen they escape, but the place of each of the 
original ones (2 to 4) is taken by 2 to 4 fresh ova. The several 
organs on the primary mesenteries of a polyp, whose calicle is 
about 32 mm. long, form ovoid masses of 6 to 9 closely adpressed 
ova. A general increase in size of the separate organs takes 
place, but this, after the ripe testes have once been formed, is 
never proportional to the general increase in size of the polyps. 
An ovary with 2 or 3 ova occupies about the same space as a ripe 
testis, and the increase is only when it comes to consist of 6 or 
more ova. The area of the nutritive endoderm increases still 
less than that of the ovary, so that in the largest polyps it covers 
the generative masses to a proportionably less degree. 
The largest specimen — of the type variety from the Maldives — 
I have examined was 40 mm. in length. A large number of the 
ova had escaped, many of the mesenteries having none. On most 
there were a number of ova, quite isolated from one another. On 
none of the mesenteries could I find any small ova to take the 
place of the escaped eggs. Indeed it seemed obvious that a 
critical period had been reached, after which ova cease to de- 
velope. No change was at this stage visible in the ectoderm, 
neither external nor of the mesenterial filaments. The whole 
endoderm was on the other hand devoid of fat and much vacuo- 
lated, even the nutritive part over the ovaries being but little 
granular. A second specimen 36 mm. long from the Cape and 
a third 33 mm. from the Maldives exhibited like conditions to the 
larger form mentioned above. 
So far I have referred only to the larger or primary mesen- 
teries, i.e. those which fuse with the stomodoeum. The smaller 
mesenteries are always of the same sex as the larger, and appear 
to exhibit the same changes. Their ovaries do not usually consist 
each of more than 3 or 4 ova. 
There is no direct proof — indeed it is only a presumption — 
that the polyp now dies. The annual (?) lines of growth are so 
regular, right up to whatever size the corallite may be, that 
obviously growth must be a very orderly process. The largest 
specimen among over 600 corallites was a Cape of Good Hope 
33 
YOL. XI. PT. 
