LIVING CORALS. 737 



LIYING CORALS. 



By W. E. DAMON. 



PERHAPS enough already has been written about corals and coral- 

 builders, but certainly too little is really known about the habits 

 and mode of growth of this interesting animal. I am fortunate enough 

 to possess tine specimens of some three or four varieties of living, 

 working coral " polyps," for such is the name by which the coral- 

 builder is designated. These specimens are kept in pure sea-water, 

 and I have studied their habits very carefully for years ; they seem 

 to be in perfect health, full of activity, and generally industrious, 

 although I can hardly observe that they have added to their coral- 

 lum during this period. A specimen of Astrangia which has been 

 described by Dana and Elizabeth Agassiz, although it has not, per- 

 haps, increased visibly in height, has enlarged in size by building 

 from its outer edges, and numbers of young and smaller polyps have 

 appeared. I have noticed that this budding and increase occur about 

 October or November of each year. 



Nothing can be more beautiful than a group of these corallets. 

 Sometimes a mass of them of three or four inches across is dredged 

 up at Wood's Hole, Massachusetts. The polyps rise high above the 

 cells, and, with their long, slender, fleecy, silk-like tentacles swaying 

 to and fro, remind one of a living bed of roses, or of a mossy bank 

 covered with heavy frost. 



I have seen the animal of a single corallet standing above the sur- 

 face of its cell an inch in height and expanded to one-third of an inch 

 in diameter, and yet many I may safely say, most people believe 

 the "coral-insect" (not an insect at all) to be a microscopic or a 

 very minute animal. Its long, snowy tentacles are covered all over 

 with warts or dots, with a larger one at the tip of each. All these 

 contain its weapons of defense, called lasso-cells, or capsule-threads, 

 with which the animal captures its prey. The smaller Crustacea, 

 coming in contact with these nettle-like arrows, are surely and sud- 

 denly disabled, and then with the longer tentacles are drawn in- 

 ward to the mouth, which is situated in the centre of all these arms. 

 This food passes into the stomach, which can be plainly seen through 

 its glass-like walls, and must be digested before the animal retreats 

 into its calicle. I have given them pieces of clams or oysters as large 

 as half a pea, which they would seize with their tentacles and readily 

 swallow. Another reason for this particular variety of coral-builder 

 being so interesting to us is, that it is the only true coral-building 

 polyp we have north of the Florida reefs, or nearer our homes than 

 the Bermuda Islands. 



Another variety, which belongs to the Oculina tribe, I have in 

 vol. xii. 47 



