Anatomy of Gorgonid.^. 141 



The typical spicules of this species are the symmetrical 

 tuberculate fusiform and the echinato-clavate. The other 

 forms figured may be regarded as only occasional. 



The basal substance offers no, features of particular interest, 

 being the same transparent homogeneous mass heretofore 

 described. There appear to be no typical stellate mesodermal 

 cells, and I was unable to discover the cells in which the spic- 

 ules have their origin. The only cells found in the mesoderm 

 of the coenenchyma are quadrate in form having large nuclei. 



Water-vascular System. The Primary canals are ar- 

 ranged around the axis cylinder in much the same manner as 

 those of Plcxaurclla dichotonia, but are not so constant in num- 

 ber, although the typical number seems to be 16, double as 

 many as are found in P. dichotonia, as is represented in PI. 

 VI, fig. 2. 



In fresh specimens these canals appear to be further re- 

 moved from the axis cylinder than in other species, and thus 

 nearer the bases of the polyps. They were seen to be richly 

 ciliated, the cilia causing rapid currents of water to pass 

 through the canals. 



The Secondary Water-vascular canals are large, numerous, 

 and conspicuous.' They are given off as branches from the 

 main canals, and ramify throughout the coenenchyma. They 

 are often seen to form a direct communication between the 

 calicles and primary canals. They penetrate the calicle walls 

 and ramify between the spicules. 



The Capillaries resemble in structure those of the species 

 already described. They appear to be particularly numerous 

 immediately under the ectodermal investment of the branches, 

 where they penetrate in great numbers through the minute 

 spaces between the cortical layer of spicules. They are also 

 numerous near the inside of the calicle wall, as if to supply 

 the polyp wall. 



Axis Cylinder. This offers no important points of dif- 

 ference from that of Muricea. There are no vermiform bodies. 



1 See PI. V, fig. I. 



