216 



ZOOLOGY 



in the interspaces between the fleshy partitions men- 

 tioned in speaking of Metridium. Since most corals, like 



FIG. 203. Coral cup of manicina. Nat. size. Photo, by W. H. C. P. 



hydroids, bud freely, and since every bud secretes coral at 

 its base, an extensive and complicated limy mass may be 

 produced. This is the way in which the brain corals and 



FIG. 204. Astranyia danse, a cluster of our Northern coral-polyps, resting 

 on limy bases of their own secretion. The animals are extremely delicate 

 and transparent. From a lithograph by Louis Agassiz's artist Sonrel. 



branching corals are formed. The only coral of the north- 

 eastern United States is Astrangia dance, which occurs 

 north to Cape Cod. It is a beautifully transparent species, 

 and forms thin encrustations of limy matter (Fig. 204). 



