28 



irregular in the upper, a few branches being more strongly developed than 

 the others. From the lower part of the stem a large number of small branches 

 are given off, and then the stem itself divides into two large branches which give 

 off similar small Ijranches. These small branches by repeated divisions give rise 

 to the polyp-bearing twigs. 



The polyps are arranged in small bundles of four to nine, and ai-e placed 

 at an obtuse angle on widely divergent stalks, about 2 mm. long. They are oval, 

 about 048 mm. high and 0-56 mm. broad. The spicules are arranged in eight 

 double rows in each of which there are five to six pairs, one of each uppermost 

 pair being much larger and projecting considerably. The lower polyp-spicules 

 average 0-24 mm. in length, the upper projecting spicule about (J-aG mm. The 

 spicules are thick spindles and have numerous warts which are less developed 

 on the projecting part. On the aboral surface of each tentacle there are two 

 rows of short rod-like spicules. 



Fig. 15.\. D. purpurea. — 

 b, from stalk cortex ; c, 

 from stalk canal walls. 



Fig. 15. D. purpurea. 



The .Stutzbundel consists of a number of large spicules of which several may 

 reach a length of 3 mm. and one may project for a distance of 1 mm. beyond 

 the polyp-head. 



Cortical spicules : {a) In the stem there are spindles curved or straight, 

 four-rayed forms, four-rayed forms in which two of the rays are rei)resented by 

 stumps, all with numerous very small regularly arranged spines. There are 

 also smooth, flat, irregular three and four-rayed forms. Several of the spindles 

 have a number of very short stumps arranged in a whorl at one end. The large 

 spindles average about \'2 mm. in length, the small about 0"18 mm. Spindles 

 of 1 6 mm. in length are present. The spicules are arranged more or less longi- 

 tudinally. 



{Ji) In the stalk there are irregular stars, spindles with one whorl of large 



