150 J- E. DuERDEN — Jamaican Adiniaria : 



parent membrane, and all the marginal tentacles come together in the centre and 

 close np the aperture. 



The jieristome is considerably elevated and usually elongated ; like the rest of 

 the disc it bears tuberculate bodies, which are here usually a little smaller. The 

 mouth is circular in small forms, elongated in larger. The stomodseal wall is 

 thrown into numerous, deep, much flattened folds, and is capable of considerable 

 eversion. It is very sharply marked o£P from the disc. Twenty folds were 

 counted in a very small specimen, and over thirty occui'red in another ; true 

 gonidial grooves do not occur (aglyphicj. 



Polyps are occasionally come upon in which the disc bears two or more distinct 

 mouths, without any indication of longitudinal fission. 



The coloration varies much in detail in different jjolyps. The column-wall 

 is light or dark brown, usually darker above, but lighter again towards the apex, 

 the latter often showing an iridescent green tinge. The disc is an iridescent green, 

 with brown, radiating lines separating it into narrow, radial areas ; or, the general 

 surface of the disc may be brown, and the radiating lines iridescent green. 



Some of the radial bands may be nearly opaque wliite. Tlie larger marginal 

 tentacles are a faint blue below, brownish or rose-coloured distally ; the smaller 

 tentacles are brown. The disc tentacles are brown and iridescent green, or may 

 be a deep blue purple. The stomodseal-walls are white. 



The dimensions are very variable. The base may be 2*5 cm. across; the 

 column 1'4 cm. in diameter, and 1 to 2 cm. high. The length of tlie larger 

 marginal tentacles is 0'2 cm. One specimen was obtained with a disc 5*4 cm. in 

 length, and length of mouth, 1'3 cm. 



Anatomy and Histology. 



The ectoderm of the base is formed of high supporting cells, along with a few 

 mucous cells. In sections the nuclei of the former give rise to a distinct narrow 

 zone, situated a little nearer the mesogloea. A very thick, brown, cuticular mem- 

 brane, which readily strips off, is still present in some examples, and is continued 

 for a short distance up the column. The mesogloea, as is the case throughout the 

 whole polyp, is very thin, and rather large ovate cells are sparsely scattered 

 through it ; a very weak musculature appears both on its ectodermal and endo- 

 dermal borders. The endoderm is much narrower than the ectoderm, and is 

 well supplied with gland cells, but devoid of zooxanthella3. 



The ectoderm of the column-wall is a high layer, and crowded with clear, 

 unicellular, mucous glands, so that an outer zone appears colourless, the contents 

 of the glands not staining. The cells are extremely delicate, and in sections are 

 ziearly always collapsed or shrunk ; indeed the tissues as a whole are less resistant 



