CORAL-MAKING POLYPS. 49 



It is obvious that the connection of the polyps in all com- 

 pound groups must be of the most intimate kind. The sever- 

 al polyps have separate mouths and tentacles, and separate 

 stomachs ; but beyond this there is no individual property. 

 They coalesce, or are one, by intervening tissues ; and there is 

 a free circulation of fluids through the many pores or lacunes. 

 The zoothome is like a living sheet of animal matter, fed and 

 nourished by numerous mouths and as many stomachs. 



Polyps thus clustered, constitute the greater part of the 

 flowering zoophytes of coral reefs. Only a few are simple 

 animals, like the Caryophyllia figured on page 42, or the 

 Thecocyathus, page 43, or the Fungia, page 46. 



This kind of budding may take place from the sides of the 

 polyp at different heights ; either (1), from the base, as in the 

 Actinia mentioned on page 40, when it is basal ; or (2), above 

 the base, when it is called lateral / or (3), at the upper mar- 

 gin outside of the tentacles, when it is called marginal or su- 

 perior ; or (4), from the disk inside of the tentacles. 



Sometimes a shoot grows out from one point only of the 

 base of a polyp, like the stoloniferous stem from a strawberry 

 plant, and at short intervals gives off buds ; and thus makes a 

 linear zoophyte with a row above of flower-animals. In other 

 cases, the base spreads in all directions and buds at the edge, 

 or in the upper surface near the edge, and so makes an in- 

 crusting plate, consisting of a multitude of polyps. 



" If the germ polyp, or that from which the compound zoo- 

 phyte proceeds, has the property of growing upward beyond 

 the adult height — which the existence of coral renders a possi- 

 bility, and even to an indefinite degree — various other forms 

 may result. 



Sometimes the first polyp gives out buds from its sides, 

 and continues so to do wbe**-it grows upward; and thus a 



4 



