61 



branches with cylindrical lower portion and flattened umbrella-like upper 



portion arise and fill up the si)ace ; in the other free space there is only a single 



branch similar to these two. From the upper surface of the flattened folds and 



partly from the stem there arise two cylindrical branches which stand at an acute 



angle to the stem, and are of considerable 



size. From the surface of the stem and 



larger branches smaller branches are 



given off at right angles to the surface ; 



these are cylindrical^ and by repeated 



divisions give rise to the polyp-bearing 



twigs. At the point of their first division 



a slight flattening occurs, and in most 



cases this is continued throughout all the 



divisions. 



The polyps are arranged in small 

 groups of four to eight, and stand on 

 stalks which measure up to '1 mm. in 

 length. They are more or less divergent, 

 but this is partly concealed by the young 

 polyps, and thus the arrangement ap- 

 proaches that of the TJttibcUaUe. On 

 the edge of the flattened branches the 

 polyps occur singly or in small groups. They are low and rounded, measuring 

 0'48 mm. in height and 0'7"2 mm. in Ijreadth, and are placed at right angles 

 to the stalk, but at times seem to be at an acute angle owing to the head being 

 slightly more bent down. The spicules are arranged in the following manner : 

 about two pairs of polyp-spicules converge, then comes a girdle of horizontally 

 placed spicules three to four deep, and above this rise eight points each con- 

 sisting of one pair of acutely converging spicules which are unequal in length, 

 and project for a considerable distance beyond the polyp. A third spicule is 

 often present and lies usually parallel to the smaller of the two. The two 

 projecting si)icules run almost parallel, diverging only near their base where 

 they are sharply bent, and in the space thus foiined between their bent portions 

 and the horizontally placed spicules, there may be a small curved spicule with 

 the convex side upwards. Another spicule occurs in the spaces between the 

 points. The lower polyp-spicules measure about 0"25 mm. in length, while 

 the upper projecting spicules average about 0"6 mm. in length. On the spicules 

 numerous thick blunt spines occur at right angles to the surface, but on the 

 projecting portion of the spicule they are directed obliquely towards the tip. 

 On the aboral surface of each tentacle two rows of densely crowded flattened 

 toothed spicules are present. 



Fig. 32. D. persica. 



