158 J. E. DuERDEN — Jamaican Actiniaria: 



tentacles have a green, blue, or brown stem, and the knob green or yellowish- 

 green, or white in one variety. Often there is a marked difPerence in colour 

 between the dicyclic marginal tentacles and the inner radiating group. The disc 

 is richly coloured ; green or blue along the radii, but towards the inner naked 

 area, dark purplish brown. The ^^eristome is briglit green ; the walls of the 

 stomodseum are white or light green. 



Specimens were jDrocured at Port Antonio in which the tip of the disc 

 tentacles was coloured bright orange red. They were associated with other 

 polyps of the more usual colours, to which they presented a marked contrast. 

 Duchassaing and Michelotti also refer to a similar variety. 



Around the Port Royal Cays two other slight colour varieties occur, also in 

 close association ; in one green and purplish brown predominate, and in the other 

 light green or grey. They are readil}' distinguishable when seen in situ in 

 patches of considerable size, the members of any one patch being alike, much in 

 the same way as has often been described for groups of Corynactis. 



The dimensions are very variable. The height of the column in extension 

 may vary from 1"1 cm. to 2"7 cm., while the diameter may be 1'7 cm. The 

 greater length of the disc of a specimen with four mouths, and also of one with a 

 single mouth, was 3 '5 cm. ; another bearing two apertures was 5-5 cm. in exten- 

 sion, with a diameter of 3 "8 cm., and a length of 4 cm. in contraction. 



The length of the marginal tentacles of the inner cycle is 0-5 cm. 



Anatomy and Histology. 



In endeavouring to remove the animal from the rock to which it is attached, 

 the base often becomes partly destroyed. Where perfect, however, the basal 

 ectoderm is seen to be formed of elongated columnar cells, which are mostly large, 

 unicellular glands, aggregated, along with the narrow sujDporting cells, around fine 

 mesogloeal processes. A thick cuticular membrane, apparently formed of coagu- 

 lated mucus, is present in some specimens between tlie ectoderm and the foreign 

 object to which the polyp is attached. 



The mesogloea of the base, like that throughout the whole J^olyp, is a thin 

 clear layer, and comparatively few cells are included within it. It stains slightly 

 with borax carmine. In regard to the abundance of tlie mesogloeal cells, the 

 species is intermediate between their practical absence in Corynactis and the great 

 quantity in most Actiniae. In the upper part of the polyp the layer is almost 

 completely homogeneous, an included cell occun-ing but rarely. In these places 

 it is indistinguishable from the mesogloea of Corynactis and the Madreporaria. 

 The endoderm of the base presents no important characteristics, and is practi- 

 cally devoid of zooxanthellse. 



