STONY CORALS; DENDROPIIYLLIA. 505 



animal, of which the Polypes are only subordinate parts. It 

 has no direct communication with their stomachs, however ; nor 

 does it appear to connect the different Polypes very intimately 

 together. But it is largely concerned in the deposition of the 

 calcareous matter of the polypidom, especially in those forms of 

 it in which the cells are connected together by a solid mass 

 (Fig. 619), instead of being seated, as in the Dendrophyllia, upon 

 the extremities of diverging branches. Even here it may be 

 observed, however, that a new twig or ramification is at first 

 produced, not by a Polype, but by a projection of the flesh, of 

 which the centre becomes consolidated, forming a cell in which 

 the Polype subsequently appears. The same takes place in the 

 early development of the gemmules. Moreover, if a piece of 

 this flesh be stripped from the surface and placed in sea- water, 

 it will begin to form a cell, by the deposition of calcareous mat- 

 ter, upon the spot where it happens to rest ; and this cell is soon 

 tenanted by a Polype like an Actinia. Many other arborescent 

 forms of lamelliform corals might be enumerated, which are of 

 great beauty to the common observer, and highly interesting to 

 the Naturalist on account of their affinity with the extinct species 

 so abundant in limestone rocks.* Amongst these are the true 

 Madrepores, in which the whole surface of the stem and branches 

 is covered with minute cells. In all these, as in the plant-like 

 Sertularidce, the living flesh is withdrawn from the lower part, in 

 proportion to the extent of growth above ; and, if attached to a 

 limestone rock, the root can scarcely be distinguished from the 

 basis on which it has been implanted. 



1073. We now pass to another series of forms presented by 

 the lithophyte corals ; those in which the Polype-cells, instead 

 of being placed on the ends or sides of branches, are distributed 

 over a continued surface, sometimes in close apposition with each t 

 other, sometimes widely separated, but united by a solid calcareous 

 mass which fills up the interspaces. Of the first of these kinds, 

 the common Astrcea affords an excellent example. We might 



* It may be desirable to remark tbat the Red Coral and its allies do not belong 

 to this group, being destitute of laminated cells. They will be described among 

 the Alcyonian Polypes ( 1093). 



