28 BRITISH FOSSIL CORALS. 
Gemmation from the wall—the lateral form—may occur at the top so as to affect the 
calicular margin, and at any place between this and the base. ‘The gemmation may be 
solitary, alternate, whorled, numerous, or irregular; and the parent may or may not grow 
after the development of the buds.’ 
The genera Cladocora, Solenastrea, Oculina, Lophohelia, Madrepora, Heliastrea, 
Stylocenia, Stylina, Astrocenia, Stephanocenia, &c., furnish examples of lateral and 
marginal gemmation. 
The basilar gemmation is especially to be observed in the genera Rhizangia, Astrangia, 
Phyllangia, and other Astrangiacce. 
Fissiparous growth.—Many corals increase in dimension and become cespitose, 
gyrate, laminar, or massive, by a repetition of a fissiparous process in the calice or calices. 
The general nature of this method of calicular division and subsequent growth may be 
seen in Plate IV, figs. 12, 13. The calice is fairly bisected through the columella or 
columellary space by the growth of two or more opposite septa, and the wall appears to 
curve inwards, whilst the parts on either side grow independently and separate with 
varying rapidity. The process may be more or less speedily repeated in the new calices, 
and as they separate and grow upwards they may or may not be enveloped in 
coenenchyma. 
Very differently shaped corals thus result. 
The genus Dichocenia offers examples of massive corals where there is fissiparous 
growth and much ccenenchyma. The genus Havia has its fissiparous individuals in close 
contact, and the species of Zhecosmilia yield long, dendroid, and czspitose forms. 
Serial growth.»—Corals of the genus Diploria, Latimeandra, Rhipidogyra, Pectinia, 
Teleiophyllia, Thysanus, Manicina, &c., have either faint traces of calices running laterally 
into each other, or else the septa follow each other in a longer or shorter series, which is 
sometimes straight, at others twisted. The occurrence of ccenenchyma, and the particular 
manner in which the “ series” may be joined laterally, determine the shape of the corallum. 
In the Latimeandre the faint traces of calices may be seen. In Diploria and Meandrinad’ 
the septa are in series, and form a massive coral ; whilst in the Ze/ecophyllia and Thysani,‘ 
where there is a long series, the corallum is simple and pedicillate. 
Gemmation occurs both in fissiparous and serial corallites. 
V.—PHYSIOLOGY. 
The ovules of corals are projected from the visceral cavity through the pyloric con- 
striction, the stomach, and the mouth, by the contraction of the tissues of the disc; and the 
cilia of the cavities assist the transit. Cilia cover the small ovule and move it onwards 
1 Plate IV, fig. 16, 17. ? Plate IV, fig. 14. 3 Plate IV, fig. 15. 
* Plate IV, fig. 14. 
