CORAL BUILDERS. 233 



over the surface, corresponds to a separate one of the 

 united polyps." 



Each individual polyp has its own separate mouth, 

 tentacles, and stomach, and they coalesce by inter- 

 vening tissues, so that " there is a free circulation of 

 fluids through the many pores, or lacunae. The 

 colony is like a living sheet of animal matter, fed and 

 nourished by numerous mouths, and as many 

 stomachs." The budding proceeds in different direc- 

 tions according to the species. In some cases the 

 base spreads in all directions, and buds at theedge, 

 so as to form an incrusting plate, in other cases it 

 has a tendency to grow upwards, budding at the 

 sides, so as to form branches, and at length a tree- 

 like form is produced, or the budding takes place 

 all over the mass, so that it maintains a more or 

 less hemispherical form, some of the masses in the 

 Pacific having a diameter, of twenty feet. Thus we 

 have the numerous forms of Orbicella, Madrepores, 

 Forties^ &c. 



But, besides this method of budding, there is 

 another and analogous process of spontaneous fission 

 by which a polyp divides in two. In such cases the 

 disk keeps enlarging until, having exceeded the 

 ordinary adult size, a new mouth makes its appear- 

 ance in the disk, a short distance from the old one, 

 growth still continues until the mouths are removed 

 further apart, a stomach is being formed beneath the 



