318 ORGANS OF DIGESTION. 



foliacious expansions, and which increase in depth towards 

 their free elevated dentated edges (110. c.), and the nu- 

 merous brown-coloured papillae, spread over the yellowish- 

 green surface of the polypi are the rudiments of the conical 

 tubular feet so largely developed on many other lithophytes. 

 From the magnitude and muscularity of the polypi in most 

 of the larger forms of lithophytes, and from the increased 

 number and strength of their prehensile organs, they are 

 adapted for seizing and digesting more highly organized prey, 

 than those delicate minute cellular forms which attract the 

 smaller floating animals by vibrating the cilia of their tenta- 

 cula. The most complicated forms of fixed polypi, and 

 those which approach the nearest in structure to the free 

 and independent actiniae, are generally those which have 

 the largest and most isolated cells, as we observe already in 

 the prominent lips and internal partitions of the polypi of 

 tubularice, and their double row of tentacula destitute of cilia. 

 In the caryophyllue, where the whole animal is sometimes 

 composed of a single polypus with its cell, as in caryophyllia 

 cyathus, the tentacula are not only disposed in a double 

 series around the flat disk of the polypi, but are also short, 

 thick, membranous and tubular as in most actinia, and 

 ciliated internally like the tubular conical feet of most echi- 

 noderma, and the corresponding hollow organs of the higher 

 zoophytes. In the turbinolia, likewise, which consists of a 

 single conical calcareous cell with thin vertical radiating la- 

 mellce, there is but one large actiniform polypus with a flat 

 disk, a transverse oral aperture, and a sub-duplicate series 

 of long tubular conical tentacula, disposed around the margin 

 of the fleshy disk; the exterior surface of these tubular tenta- 

 cula is sometimes irregularly tuberculated, like those of 

 many inferior vaginiform zoophytes, and as we perceive in 

 those of the simple hydra. The polypi of fungia more 

 closely resemble actinia than those of any other lithophyte, 

 as seen in those of fungia actiniformis (Fig. 111. A.) and 

 fungia crassitentaculata (Fig. ill. B.), from the South 

 Pacific. In these broad expanded isolated polypi, envelop- 

 ing a solid lamellated calcareous axis (ill. D. C.), the 

 transversely-elongated central mouth is lobed on the margin 

 (111. A.), or surrounded with lively-coloured tubercles (ill. 

 B.), as in many actiniae ; and the whole surface of the fleshy 



