CLASS I ANTHOZOA Tit 
(Euthecalia). In many eases the peripheral edges of the septa become thickened 
and laterally fused to form a spurious theca (Pseudothecalia) ; and occasionally 
the dissepiments lying in a certain zone become united so as to form an inner 
wall within the true theca. The epitheca is a usually smooth, sometimes 
corrugated, superficial calcareous investment, which, according to Koch, is 
merely a prolongation of the basal plate, and is secreted by the outer surface 
of the ectoderm, which is reflected over the top of the corallum. The epitheca 
is deposited either directly upon the theca, or, when the septa are produced 
outwards so as to form exothecal lamellae or ribs (costae), the theca and epitheca 
are separated. Exothecal lamellae, not corresponding in position to the septa, 
are called pscudocostae or rugue. 
Sexual reproduction is comparatively rare among Anthozoans. Following 
fertilisation and segmentation of the ova, ciliated larvae are born, which swim 
about for a time, ‘become fixed, and develop into simple polyp individuals. 
Asexual reproduction by gemmation or fission is much more common. The 
individuals produced in this way remain connected with one another and with 
the parent animal, forming polyp stocks or colonies of exceedingly various 
forms and sizes. 
New corallites are produced either within or without the calice of the 
parent polyp. In eatra-culicinal gemnution, the buds are thrown out either from 
the sides of the polyp (lateral gemmation), or are formed in the common 
calcareous matrix which unites the various corallites of a colony (coenenchymal 
and costal gemmation). In both cases the new corallites may diverge from one 
another, being attached to the parent corallum only at the base, or they may 
grow up closely opposed to the latter and to one another, so that the thecae 
are in contact on all sides. In this way, branched, dendroid, or massive and 
knob-like (‘‘astraeiform”) compound coralla are formed. A less common 
mode of increase is by /asal or stolonal gemmation. In this process the wall of 
the original polyp sends out creeping prolongations (stolons) or basal expansions, 
out of which new corallites arise. In calicinal gemmation buds are produced 
within the calice of the parent corallite, according to one or the other of the 
following methods :—Either certain particular septa become enlarged and_pro- 
duced so as finally to enclose a new calicinal disk (septal gemmation) ; or tabulae 
are produced upwards in the form of pockets, from which new corallites are 
developed (tabular gemmation). In both septal and tabular gemmation, a portion 
of the parent corallite including a part of the original wall is concerned in the 
formation of buds; while the septa or modified tabulae are converted into 
portions of the new ’ thecae, from which new septa then begin to grow inwards 
toward the centre. 
A peculiar kind of calicinal gemmation is that known as rejuvenescence. In 
this method only one bud is formed within the parent calice, but it enlarges 
until it completely fills the latter. By the indefinite repetition of this process, a 
corallum is formed, consisting of a succession of cups placed one within the other, 
of which only the youngest and uppermost is occupied by the living animal. 
The beginning of reproduction by jission is marked by an elongation or 
distortion of the parent calice, accompanied by the contraction of the wall 
opposite points along the margin. The constriction may proceed until it 
divides the oral disk into two halves ; or two opposite septa may unite to form 
a new theca. By this method, branching, massive, or astraeiform colonies are 
produced, which do not differ essentially from those formed by budding. 

