CORALLINES. 



133 



is not equally distributed, but separated into zones more or less deep 

 in colour, containing very thin preparations which crack, not irre- 

 gularly, 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 corpuscles occur, charged with irregular asperities, much 

 redder than the tissue into which they are plunged. These are much 



Fig. 54. Birth of the Coralline Larvae. (Lacaze-Duthiers.) 



more numerous in the red than in the light band, and they necessarily 

 give more strength 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, ac- 

 cording to this able observer, the polyps of the same colony are all 

 either male or female, and the branch is unisexual ; in others there 

 are both male and female, when the branch is bisexual. Finally, but 

 very rarely, polyps are found uniting both sexes. 



The coral is viviparous ; that is to say, its eggs become embryos 

 inside the polyp. The larvae remain a certain time in the general 



