86 



tinuous surface. It consists of a large number of small branches of almost 

 ecjual length. The branches on one side show a slightly larger growth and 

 there is thus a hint of development in one plane. The branches are rounded 

 and give rise by repeated divisions to the polyp-bearing twigs. 



The polyps are arranged in groups of five to nine, but seven is the com- 

 monest number. They also occur on the lower branches in smaller groups and 

 even singly. They are low and round, measuring 0'48 nun. in height and 072 



mm. in breadth, and are placed almost at right angles 

 on the stalk, which may reach a length of 1'5 mm. 

 The spicules are arranged in eight doul)le rows in 

 each of which there are seven pairs of converging 

 spicules ; the uppermost pairs may be slightly larger 

 and project beyond the polyp. The spicules are 

 spindles, straight or curved, with few protuberances 

 on the surface ; they average 0-24 mm. in length, 

 while the upper projecting spicules may reach a 

 length of 032 mm. On the aboral surface of the 

 tentacles there are two rows of bluntly converging 

 spicules, the ends of which are roughly alternate. 



The Stutzbiindel is well developed ; one of the 

 spicules is usually much larger than the rest and pro- 

 jects for a considerable distance beyond the polyp- 

 head. It may be 3-3 mm. long and project 104 mm. 

 Cortical spicules : {a) Those of the stem are straight or curved spindles, 

 covered with numerous blunt warts ; they vary in length from 048 to 33 mm. 

 and in breadth from 0-048 to 0"48 mm. 



(h) In the stalk there are spindles, clubs, rods or bars, rayed forms, and 

 numerous irregular forms. They are all covered by very pr'ominent rough 

 warts, and on the spindles blunt spines also are usually found. The spindles 

 vary from 0-24 to 0-8 mm. in length, and from 01 1 to 017 mm. in breadth. 



Canal-wall spicules : {a) In the stem there are spindles, either straight or 

 sharply curved, covered with rough warts. They vary in length from 43 to 

 r7 mm. and in breadth from 0"11 to 024 mm. 



{b) In the stalk there are spindles, either straight or curved, three- and four- 

 rayed forms, and a number of irregular, slightly globular forms. They are 

 all thickly covered by very rough warts. The spindles measure from 4 to 

 1 -6 mm. in length, and from 0-16 to 024 mm. in breadth. The three- and four- 

 rayed forms are almost of the same length as the spindles. Of the I'ayed 

 forms two or three of the rays are in several cases short and thick while 

 the i-emaining ray is long ; in others, one of the rays may be short and the 

 others of equal length. 



Pig. 42. D. elegans 



