ZOOLOGY OF THE BERMUDAS. 117 



concealed. The average height of the specimens is about 15 

 cm. and the breadth nearly the same, and thus D. Bermudensis 

 is decidedly smaller than D. ddimtvla. The ectoderm has been 

 almost entirely macerated away, so that the external surface of 

 the mesogloea is exposed to view. This presents numerous 

 transverse folds due to contraction, but in addition fine linear 

 depressed striae are present, both horizontal and longitudinal, 

 dividing the surface into numerous rows of small quadrangu- 

 lar elevations visible to the unaided eye. The color through- 

 out is a dirty-green. 



The base is adherent, flat, and about the same size as the 

 column. It is marked by radiating and concentric strise, con- 

 tinuations of the longitudinal and horizontal strias respectively 

 of the column. No verruc;i5 or tubercles occur on the column, 

 though the quadrangular areas produced by the strise are 

 slightly more prominent toward the margin. This is well 

 marked and smooth, and is separated from the tentacles by a 

 deep fosse (collar), near the bottom of which are about 12 short 

 digitiform fronds about 1 mm. in height. (PI. 10, fig. 4p, and 

 PI. 11, fig. 1.) 



Between these fronds and the tentacles there is upon the 

 endodermal surface of the collar a sphincter (PI. 10, fig. 4, sp) 

 of the diffuse type, which differs markedly from that of D. 

 delicatula, the mesogloeal processes being much more delicate, 

 and anastomosing somewhat in their proximal portions (PI. 

 11, fig. 2). The circular muscles of the column wall external 

 to the digitiform fronds are fairly prominent, and are con- 

 tinued the entire way down the column, not enlarging however 

 to form a second sphincter. 



The tentacles are simple, conical, and of moderate length, 

 and are arranged in four cycles, their number being probably 

 96. By actual count they seemed to vary somewhat, usually 

 falling below that number, but the discrepancies are probably 

 due to the difiiculty of making a correct enumeration. They 

 possess well-developed mesogloeal processes for the support 

 of the ectodermal muscles. The disc is deeplv folded in, iu- 



