232 THE OCEAN WORLD. 
well-developed polyps, and particularly those with branching extre- 
mities, in which this phenomenon is produced. The new beings 
resemble little white points pierced with a central orifice. Aided by 
the microscope, we discover that this white point is starred with 
radiating white lines, the edge of the orifice bearing eight distinctly- 
to-be-traced indentations. All these organs are enlarged step by 
step until the young animal has attained the shrub-like or branched 
aspect which belongs to the compound polypidom. The tube is 
branching, and the orifices from which the polyps expand become 
dilated into cup-like cells. 
The coral of commerce, so beautiful and so appreciated by lovers 
of bijouterie, is the polypidom. 
It is cylindrical, much channeled 
on the surface, the lines usually 
parallel! to the axis of the cylinder, 
the depressions sometimes corres- 
ponding to the body of the animal. 
If the transverse section of a poly- 
pidom be examined, it is found to 
be regularly festooned on its cir- 
cumference. Towards its centre 
certain sinuosities appear, some- 
times crossing, sometimes trigonal, 
sometimes in irregular lines, and 
in the remaining mass are reddish 
folds alternating with brighter 
Fig. 89.—Section of a Branch of Coral. spaces which radiate from the 
oe Dmiee) centre towards the circumference 
(Fig. 89). In the section of a very 
red coral, it will be observed that the colour is not equally distributed, 
but is separated into zones more or less deep in colour, containing 
very thin preparations which crack, not irregularly, but parallel to 
the edge of the plate, and in such a manner as to reproduce the 
festoons on the circumference. From this it may be deduced that 
the stem increases by concentric layers being deposited, which 
mould themselves one upon the other. In the mass of coral 
certain small bodies (spicules) occur, with irregular asperities, much 
redder than the tissue into which they are plunged. ‘These are much 
more numerous in the red than in the light band, and they necessarily 
give more colour to the general tint. 
To the mode of reproduction in the coral polyps, so well described 
by Lacaze-Duthiers, we can only devote a few lines. Sometimes, 
