CORALS AND CORAL MAKERS. 



35 



ORBICELLA CAVERNOSA. 



begin to exceed the width usual to the species, a new mouth 

 opens, commencing a new polyp ; and thus the growth of the 

 mass involves multiplication by buds. The small calicle near 

 the centre of the figure is from 

 one of the new interstitial buds. 



Species of Pontes also grow 

 into hemispheres and rude hil- 

 lock-like forms, through the 

 same method of budding, and 

 some of the masses in the tropi- 

 cal Pacific have a diameter ot 

 even twenty feet. Myriads ot 

 living polyps are combined in a 

 single such mass, for each is but 

 a fifteenth or a twentieth of an inch in diameter. 



Often there is a lateral growth of the polyp and thereby of 

 the zoophyte without much upward growth; and spreading 

 leaves are thus made, and bowl-like shapes. Where there is 

 lateral budding, the leaves have generally an edge of young 

 polyps from the new buds that are there opening, as in the 

 Gemmipores, and some foliaceous Madrepores ; where there is 

 superior budding, and sometimes in the case of inferior, the 

 new polyps appear some distance from the edge, the growing 

 margin spreading on in advance of the buds that open in it, as 

 in the Echinopores. 



Besides the method of budding explained in the above re- 

 marks, there is also a kind of superior budding called sponta- 

 neous Jission^ which consists in a spontaneous subdivision of a 

 polyp, by which two are made out of one. In such cases the 

 disk of the polyp has not a distinct limit of growth, as in the 

 above, but tends to enlarge indefinitely ; and when there is a 

 beginning of an increase beyond the proper adult size, a new 

 mouth opens in the disk, a short distance from the old one, 

 and at the same time its edges extend downward and make a 

 new stomach beneath it; finally tentacles are developed between 

 the two mouths, and then each polyp separates with its part of 



D 2 



