89 



The stalk is short, about 2 cm. in length, thick and fairly rigid. It is 

 granular in appearance and gives off a large number of "stolons which are often 

 branched. 



The polyjmrium is rounded in form, compact in appearance and regular 

 in outline. From the lower i)ortion of the stem a large number of small 

 branches are given off, then the stem divides into three main portions which 

 stand out almost at right angles to the stem. 

 Each of these divides into smaller branches 

 which by division give rise to the polyp- bearing 

 twigs, and also gives off small branches similar 

 to those on the lower part of the stem. These 

 branches also give rise to knob-like projections 

 at the to]) of the colony, which is somewhat 

 flattened on its summit and on one side. Some 

 of the lower branches show a slight flattening 

 in the stalk and a more marked flattening in the 

 upper portion, or the upper portion is slightly 

 flattened while the lower portion is not. 



The polyps are arranged on short stalks in 

 small groups of six to fourteen on the upper part, 

 but in the lower part they may occur singly or 

 in small groups of two to five each. In the 

 upper jjortions several of the small groups may 

 be in close contact, thus forming a large group. 

 The polyps are small, averaging 0"55 mm. in 



height and Oo mm. in breadth, and are placed on the stalk, 1 mm. in length, 

 at an obtuse angle. The spicules are arranged in eight double rows ; in the 

 lateral rows there are six pairs of spicules, and in the dorsal rows there are 

 four to five pairs. The uppermost spicules may be longer than the others 

 and project beyond the polyp. The lower polyp-spicules are about 030 mm. 

 in length, the upper about 0"42 mm., projecting about 0"24 mm. beyond the 

 polyp. They are flattened spindles either curved or straight, or, in the case of 

 the ui)per, sharply bent near one end, and covered with spines which are directed 

 obliquely towards the tip on the projecting part. 



The .Stutzbiindel is well developed, one of the spicules usually projecting 

 for a considerable distance, 08 mm., beyond the polyp and reaching a length 

 of 3-0 mm. The tips of two more may be seen projecting slightly beyond the 

 polyp. In other cases the spicules are smaller and more numerous, their tips 

 meeting at an angle and projecting slightly beyond the polyp. 



Cortical spicules : («) In the stem there are slender spindles either curved 



or straight, with numerous regularly arranged blunt spines which may be 

 12 



Fig. 44. D. tripartita. 



