132 THE OCEAN WORLD. 



secondary system of network, which brings them into direct commu- 

 nication with the polyps. The alimentary fluids elaborated by the 

 polyps pass into the branches of the secondary and irregular network 

 system, in order to reach the great parallel tubes which extend from 

 one extremity of the organism to the other, serving the same purpose 

 to the whole community. 



When the extremity of a branch of living coral is torn or broken, a 

 white liquid immediately flows from the wound, which mingles with 

 water, and presents all the appearance of milk. This is the fluid 

 aliment which has escaped from the vessel containing it, charged with 

 the debris of the organism. 



What occurs when the bud produces new polyps ? It is only round 

 well-developed animals, and particularly those with branching ex- 

 tremities, 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 radia- 

 ting white lines, the edge of the orifice bearing eight distinctly-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 polypi 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 depres- 

 sions sometimes corresponding to the 

 body of the animal. If the transverse 

 section of a polypidom be examined, 

 it is found to be regularly festooned 

 on its circumference. Towards its 

 centre certain sinuosities appear, 

 sometimes crossing, sometimes tri- 

 gonal, sometimes in irregular lines, 



Fig. 53. Section of a Branch of Coral. -, . ., . . , 



and in the remaining mass are red- 



dish folds alternating with brighter 



spaces which radiate from the centre towards the circumference (Fig. 53). 

 In the section of a very red coral, it will be observed that the colour 



