3i6 



THE POPULAR SCIENCE MONTHLY. 



from the rocks ; lay them in your basket, with plenty of wet sea-weeds ; 

 break from the rock some fragments with the sea-weeds still growing 

 upon them ; on your return to your studio put the whole into your 

 aquarium, well supplied with pure sea-water. At first, the sea-anemones 

 will appear like so many mere lumps of soft flesh, without definite form. 

 But leave them there for a night ; and, when you look again, vou will 

 find each one has established itself, and has expanded into a thing 

 of beauty. 



Those polyps which form the beautiful clusters of coral that adorn 

 our mantels and museums, and which build up the vast coral-reefs and 

 islands, differ in only one important respect from the sea-anemones. 



Fig. 9.—Sarsia (Coryne) mirabilu ( Agasfiz). CIus 

 ter of Hydroids growing on sea-weeds. 



=^ 



Fig. 10.— Single individual of Fig. 9 enlarged, 

 showing a b jiT^t ready to become free 

 .ielly-fishes or Medii?se ; Fig. 11, c, young 

 bud. 



Fig. 11. 



-Sarsia {Coryne) miralilis (Agassiz). 

 Adult, Massachusetts Bay. 



The sea-anemones are wholly soft ; they secrete no skeleton, or only 

 the merest particles of hard matter. On the other hand, the coral-pro- 

 ducing polyps secrete a stony skeleton. The old notion that coral is 

 something built by an insect is entirely erroneous. The coral-producing 

 animal is in no sense an insect, nor does it toil to build the clusters and 

 reefs of coral which it forms. The coral-polyp lives and eats, and the 

 getting of its food is the only labor of its life. 



