Growth, and Habits of Coral Zoophytes. 61 



nearly reached the surface, and was quite immovable, and 

 some had grown over the others. Mr Stutchbury describes 

 a specimen, consisting of a species of oyster, whose age could 

 not be over two years, encrusted by an Agaricia, weighing two 

 pounds nine ounces.* It is stated by M. Duchassaing, in a 

 letter from Guadeloupe, that in two months some large indi- 

 viduals of the Madrepora proUfera, which he broke away, were 

 restored to their original size.f 



Since the return of the expedition I have received a letter 

 containing some facts on the growth of Actiniae from Sir J. 

 G. Dalyell, whose able observations in this department of 

 science are highly curious and important. After speaking 

 of the various conditions and sizes of the young at birth, and 

 of the difference in the rapidity of growth depending on the 

 amount of nutriment at hand, he says, speaking of a Scottish 

 species of Actinia, " The dimensions will generally double in 

 a fortnight from its birth. The diameter of the base being 

 originally about an eighth of an inch, or hardly as much, 

 will be five-eighths in six months ; and the tentacles will 

 occupy a circle of an inch and a-half in diameter. In 

 twelve or thirteen months the diameter of the base will 

 reach an inch, and the expansion of the tentacles two inches 

 between the tips. An Actinia, whose tentacula expanded 

 a quarter of an inch three weeks after it was produced, 

 enlarged so much in five months that they expanded an 

 inch, and the body was then half an inch thick." If we 

 reason upon these data, and assume that the Madrepore 

 polyps may increase lineally in six months as much as the 

 young Actinia, we shall have an elongation of five-eighths, 

 or three-fourths of an inch in six months. Taking the still 

 more rapid rate of doubling in a fortnight, which might be 

 more correct, since the Madrepore polyps are about the size 

 of the Actinia in its earliest state, we should have a lengthen- 

 ing of a fourth of an inch in a month, and three inches a 

 year. The data upon which this conclusion is based, though 

 important, are uncertain, but would probably give too high 



* West of England Journal, vol. i., p. 50. 

 t L'Institut, No. 639, April 1, 1846, p. 111. 



