POLYPIFERA. 



Fig. 38. 



Fungia. A. portion of the calcareous basis has been denuded of the gelatinous coating. (After Forskal.} 



settle down again at the bottom in its right 

 position. 



The living gelatinous crust which covers 

 the surface of the lamella is not merely a su- 

 perficial investment, as it has been described 

 by some writers, but, as will be proved here- 

 after, enters essentially into the formation of 

 the substance of the stony mass, upon the 

 component parts of which it exerts a vital 

 influence. 



The Fungia described above inhabits the 

 Red Sea, and is entirely destitute of tenta- 

 cular appendages ; but the generality of those 

 brought from tropical climates have their 

 upper surface covered with numerous cylin- 

 drical tentacula (Jig- 39), which, when ex- 

 panded, give it very much the appearance of 

 a true Actinia. When these tentacula are 

 touched, they shrink, and partially hide them- 

 selves between the radiating lamellae. The 

 stony polypary has in this species been proved 

 to be in reality lodged in the interior of the 

 animal's body, the soft parts of which cover 

 the lower surface as well as the upper, and 

 even form a fleshy ring around the margin of 

 the disc, giving the idea of the foot of an 

 Actinia. 



In the centre of the upper surface there is 

 an oval aperture (fig- 39), which has been 

 regarded as the creature's mouth ; but there 

 does not seem to be any stomachal cavity. 

 The tentacula of some species are so large, 

 that they look something like leeches ; they 

 have, however, no terminal orifice, as those 

 of the Actiniae have, but seem to fill them- 



selves with water by a kind of interstitial 

 absorption. 



The polype-like investment of a Fungia of 

 this description * is fleshy, membranous, and 

 flattened, generally circular or oval, having in 

 its centre an elongated opening ; the animal is 

 thicker at this part than at the circumference. 

 The Fungia then is a broad polype, slightly 

 fringed around its margin, and secreting, by its 

 inferior surface, calcareous matter, imitating 

 all the natural forms of the animal, and even 

 its accidental positions. All the septa are tri- 

 angular, much thicker at their base than at 

 the summit, where the fleshy crust is so thin, 

 that if the polype is colourless it is im- 

 perceptible; but it is distinct in coloured 

 species. Upon the sides of the laminae are 

 little tubercles, which, penetrating the fleshy 

 folds of the animal, cause it to adhere so 

 firmly to the calcareous basis, that it is impos- 

 sible to detach it, except by piecemeal. In 

 the natural state, the mouth of the polype is 

 prominent, but it does not project beyond the 

 fissure which contains it ; at the least touch 

 the whole creature contracts, so that it would 

 seem that there was no animal. During 

 growth, as the lamina? become more elevated, 

 the interstices are gradually filled up from the 

 bottom ; but the increase of the Fungia in 

 thickness is very limited, as, in fact, is its 

 lateral extent, the diameter rarely exceeding 

 six or seven inches. 



Generally the gemmules of Fungiae are de- 

 veloped upon the sand, without, however, ad- 

 * Quoy et Gairaard, Voyage de 1'Uranie. 



