Part II. — Stichodactylince and Zoanthece. 169 



brown ; more centripetally, it is divided into narrow, radiating areas separated by 

 dark lines. Each area consists of distinct, opaque white patches, or of continuous, 

 opaque white bands, and corresponds with the rows of tentacles. The central, 

 naked part of the disc is darker, and usually shows a purplish tinge, and a few 

 white flecks may be scattered about. The margin of the lips is a stronger purple. 

 The tentacles, both in different regions of the disc, and even in different parts of 

 the same tentacle, also vary considerably. At their origin the short stems are of 

 much the same colour as the j^ortion of the disc from which they arise. Many of 

 the inner show an opaque wliite circle at the place of origin. The tips of most are 

 strongly coloured ; at their thickest part is an ojDaque white annulus, while the 

 area immediately above may be greyish, yellowish-brown, or iridescent green. 

 The last-mentioned condition is usually exhibited by the jDcripheral cycles, and 

 the first cycle of this series often projects slightly beyond the others, its tentacles 

 having intensely opaque white tips, wliich give a marked peculiarity to the colour- 

 pattern of the disc. Usually the tips of the internal tentacles are whiter than those 

 of the outer. At any part of the tentacular area, larger, bright green tentacles 

 may occur. 



The capitula of all the tentacles of several specimens obtained near the bathing 

 place at Port Antonio were a bright-green, and the white opacity on the disc was 

 absent, the whole surface, except the purple peristome, being a rich dark brown. 



As mentioned by Duchassaing and Michelotti, the brighter colours are 

 sometimes evanescent or may undergo modification. The rich, tentacular colours 

 of some specimens kejDt in the laboratory, and exposed to the full sunlight for a few 

 hours, practically disappeared, the whole disc and tentacles being reduced to a 

 thin, opaque white and delicate brown. Others, especially those not so brightly 

 coloured, showed no alteration. 



The diameter of the expanded disc, in the living condition, varies from 10 to 15 

 cm., or may even expand to as much as 20 cm. The diameter of the column may 

 be about 6 cm., but depends much upon the amount of distension ; the height is 

 from 7 to 8 cm., but in a tall jar in the laboratory the column elongated to as 

 much as 9 or 10 cm., and swayed to and fro. The length of the tentacles 

 is 0*4 cm., and the greatest diameter, which is towards the tips, is 0'2 cm. The 

 disc of specimens preserved in formol is about 5*5 cm. in diameter, and the 

 column about 3-5 cm. in height, and the same in diameter. 



Anatomy and Histology. 



The basal ectoderm is a broad layer, constituted mostly of supporting 

 cells, among which are a few granular gland cells. The mesogloea is usually 

 narrower than the ectoderm, and is finely fibrous in character, with 



