63 



and these again divide in a roughly dichotomous manner into smaller branches 

 or twigs which bear the polyps. The arrangement of the leaf-like branches is 

 noteworthy— both are very large and form a collar almost surrounding the 

 stem, leaving only two small spaces, at each of which a much smaller branch 

 arises at a slightly lower level ; but 

 these smaller branches, although ap- 

 pearing leaf-like owing to their flat 

 upper portion, have an almost cylindri- 

 cal lower portion, in contrast to the 

 two larger branches whose origin is 

 almost as broad as the flattened portion 

 and which may be called well-developed 

 folds of the outer siuface. Smaller 

 branches are given off from the upper 

 surface of these, as from the stem and 

 its main branches. 



From the ends and sides of the 

 twigs and from the edges of the 

 flattened branches the polyps arise in 

 small bundles of three to eight indi- 

 viduals and are placed on widely 

 diverging stalks. The divaricate nature 

 of the bundles tends to be masked 



by young polyps which arise at the base of a polyp-stalk or in the angle be- 

 tween two stalks. A noteworthy feature is that there are apparently two 

 kinds of polyps, (i) a larger with very well-developed Stutzbundel, and (ii) 

 a smaller, with a weak Stutzbundel or with none. This apparent dimorphism 

 is simply due to the juxtaposition of adult and young polyps. The polyps are 

 small, measuring on an average 0'45 mm. long and 0'45 mm. broad, and are 

 placed practically at a right angle on the stalk, which is slightly less than 

 1 mm. in length. The polyp-spicules are arranged in eight double rows in each 

 of which there are five pairs of converging spicules, one or both of the 

 uppermost pair being longer, and, especially in the lateral rows, projecting be- 

 yond the polyp-head. The lower spicules are 030 mm. long, while one or both 

 of the uppermost pair may reach a length of 1 mm. and project for a distance 

 of 06 mm. All these have short, simple, regularly arranged thorns, which on 

 the projecting tips show a tendency to upward direction. 



The Stutzbundel spicules are enormously developed and form a shield for 

 the back of the polyp-stalk. They are usually four to five in number, one of 

 which is generally especially long ; the longest may reach a length of 4 mm. and 

 a breadth of 0"18 mm. and project for a distance of 1-2 mm., but the average 



Fig. 33. D. dichotoma. 



