7 



360 Observations in reply to Mr. Lonsdale's " Remarks" 



of the Endopachys. This character according to my observations, 

 is one of the least important among corals. In Astraea, Pocil- 

 lopora as well as Dendrophyllia, (and also other genera,) there is 

 every variety in this character, from the most solid, to the most 

 cellular texture. The same species at times is full of pores in the 

 early state and becomes quite solid in a more advanced condition. 



From the manner in which the coral is secreted, it is also obvi- 

 ous that the character cannot be important. The secretions take 

 place among the tissues, beneath the skin. They are sometimes 

 so general as to form a solid texture without visible pores, and m 

 other cases, where certain of the animal fibres do not add to the 

 secretions, there are pores larger or smaller, occupied by these 

 animal tissues. These tissues form a communication between the 

 interior and exterior; they occur in the most compact coral 

 though not visible except in thinly polished fragments examined 

 with a lens, or after digestion in an acid which removes the cal- 

 careous material. After the coral is begun in the young animal, 

 it is constantly receiving addition to its surface. A common 

 mode, illustrated in the species of the genera Madrepora, Den- 

 drophyllia and others, consists first in the secretion taking place 

 in points, so as to raise minute prominences on the surface ; and 

 next, after the points are more or less elongated, the secretion 

 becomes more general, and all the points are connected by the 

 calcareous secretions, which thus make a net- work or layer, over 

 the whole. In a transverse section of most Madrepores, the suc- 

 cessive series of minute columns are well shown. In the Dendro- 

 phyllias referred to, and even in some specimens of the D. ramea 

 the same structure is apparent. When the points are obsolete, 

 the coral will consist of layers of lime, as is sometimes apparent. 

 Often again there is no regularity or approach to layers in the po- 

 rous structure, as in D. scabrosa, &c. 



As the animals grow, the pores which contain living fibres in 

 the young state, often gradually diminish by the secretions from 

 the surface of these fibres, which themselves are gradually dis- 

 appearing, and the coral which was before very porous may 

 finally become solid. Almost every genus illustrates this point 

 The exterior fleshy part of the animal is in no sense " a mantle, 

 (any more than the skin of an Actinia,) and it is not known e\e 

 to extend itself over a part once dead. ... n 



If Mr. Lonsdale means simply by " thickening from within^ 

 that nourishment and calcareous material are distributed ont ^ s 

 from the visceral cavity, (which I suppose is not precisely w 

 view,) then his character will apply to nearly all coral zoopo y ?® .^J 

 for all cellular coral species have free circulation of the cny 

 fluids wherever there are tissues, and these fluids are den . 



from the stomach and visceral cavity ; and the invisible nore 

 tu a w, — _-i-j ■ , .'.'.,. » l- . M-hetner*' 



i 



species 

 character is 



