CORALLINM. 



233 



according 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 larva remain a certain time in the general 



Fig. 90. — Birth of the Coral Larva. (Lacaze-Duthiers.) 



cavity of the polyp, where they can be seen through its transparent 

 body, as exhibited in Fig. 90. Aided by the magnifying powers of 

 the microscope, coral larvae may even be examined through the trans- 

 parent membranous envelope. From this position they escape from 

 the mouth of the mother in the manner represented in the upper 

 branch. The larva then resembles a little white grub or worm, more 

 or less elongated. The larva is, however, still egg-shaped or ovoid; 

 moreover, it is sunk in a hollow cavity, and covered with cilia, by the 



