ACTINIANS FROM THE BAHAMA ISLANDS 105 



In the contracted condition the animal is generally somewhat 

 flattened, measuring in height 1.5-2.0 cm., and in diameter about 2 cm., 

 the base being usually a little smaller than the upper part of the col- 

 umn. Dr. Northrop's notes contain no statement as to the coloration 

 of the living animal, but according to Duchassaing and Michelotti the 

 mouth is white, surrounded by a band of brilliant yellow, and the ten- 

 tacles have the appearance of white glass. 



The mesogloea of the column walls is rather thin, and in much con- 

 tracted forms may appear as if provided on its endodermal side with 

 numerous distinct processes, which give to the column wall a ridged 

 or checkered appearance. Toward the upper part of the column are 

 numerous cinclides, not readily distinguishable in all preserved speci- 

 mens and apparently without any very definite arrangements, though 

 they are confined entirely to the upper part of the column, none being 

 found below the middle. 



There is a distinct collar and fosse in the preserved specimens just 

 above the cinclidal region of the column, and at that portion of the wall 

 which forms the floor of the fosse the endodermal muscle processes 

 are considerably higher than elsewhere in the column wall, and form 

 what may be termed a diffuse endodermal sphincter. The true 

 sphincter lies, however, higher up, just below the point where the tenta- 

 cles arise, and is a weak structure embedded in the mesogloea, which is 

 hardly appreciably thickened for its reception. It consists of a few 

 rather scattered cavities, arranged practically in a single row and con- 

 taining the remains of muscle cells ; it is not strong enough to produce 

 complete inclosure of the tentacles. 



On account of the position of the sphincter the collar .cannot be 

 regarded as the margin. Indeed there is no distinct margin, the upper 

 part of the column wall passing directly over into the bases of the 

 tentacles, so that, in the usual formula, it is necessary to say that the 

 margin is tentaculate. The tentacles are rather numerous, apparently 

 somewhere in the neighborhood of 192, though an accurate count is 

 difficult in the preserved specimens on account of the manner in which 

 the cycles are crowded together towards the margin. They vary some- 

 what in length in the various specimens I have examined, owing to dif- 

 ference of contraction, but the average may be put at i cm. The most 

 interesting feature of the tentacles is, however, the occurrence upon them 

 of a large number of spherical protuberances scattered over their sur- 



