Mr. J. E. Gray's Outline of an An-angement of Stony Corals. 123 



Museum' for 1842 I observe, "the form of the masses (of coral) 

 appears to be greatly influenced by the position in which they 

 have grown, and the size of the individuals (cells) greatly depends 

 on the quantity of nourishment they are able to procure. This 

 is proved by the fact, that if all the individuals of the same mass 

 are equally exposed they are of equal size, but if the surface of 

 the coral is waved as in Explanaria, the individuals on the 

 convex part of the mass which could procure the most food are 

 large, while those on the concave or sunken parts are small,'' 

 p. 131. Continued experience and the examination of many 

 hundred specimens have only extended and confirmed these opi- 

 nions ; consequently I expect that many of M. Ehrenberg's new 

 species are what are only regarded in this paper as varieties : for 

 example, he has described six species of Seriafopora ; I have ex- 

 amined many specimens from different localities presenting dif- 

 ferences of size and of comparative thickness and length of the 

 branches, but am inclined to consider them as all varieties of the 

 same species*. 



It is a common error to regard the whole mass of a Brainstone, 

 for example, as a living mass ; this is by no means the case ; it is 

 only a very shallow coat on its outer surface, which is alive at 

 one time ; for as the animal increases in size above, the deposition 

 of calcareous matter continues advancing below, and when that is 

 completely deposited it is of no further use to the animal but as 

 a support, and has no longer any organic life, for this part is in 

 fact buried in its o\vn secretion. This is the case with most of 

 the coral animals, it is only the end of the CaryophyllcB or Dendro- 

 phyllaef about as deep as the cavity of the cell, that is alive ; the 

 other part being merely a peduncle to support the animal. This 

 is well seen in the Oculina virffinea, where the older branches of 

 the coral often become tubular. 



This structure is further exhibited by the fact, that when any 

 part of a massive coral is injured and the animal destroyed, the 

 injured part is healed over by the lateral development of a thin 

 layer of coral, which is not to be distinguished in appearance 

 from the normal structure of the coral. 



In general the edge of the cell and the laminse within it are 

 calcareous nearly to the surface of the animal, and in many of 



* Since this paper has been in type, Mr. Forbes has kindly lent me a 

 volume by Mr. Dana on the Structure and Classification of Zoophytes (Phi- 

 ladelphia, 1846), containing some very interesting observations on these 

 animals made during the United States' exploring expedition. Mr. Dana's 

 classification of the stony corals is only a slight modification of that pro- 

 posed by M. Ehrenberg. The three works I have quoted have each a very 

 different character ; — the French clear, calm and minute ; the German 

 theoretical, almost mystical, and difficult; the American oratorical and 

 high-flown. 



9* 



