94 



rounded and thick, and give rise by repeated division to the polyp-bearing 

 twigs. From the general surface of the stem small branches also arise. 



The polyps are arranged in groups of four to twelve, which are again 

 arranged in larger groups, the surface of which is either flat or slightly convex. 

 They are low and oval, measuring from 032 to 0<}4 nnn. in height and from 

 0-48 to 08 mm. in breadth, and are placed at a very obtuse angle on the stalks 

 which measure up to 1-2 mm. in length. The spicular arrangement differs 



slightly so that there are two types present. 

 In all there are eight double rows in each 

 of which there are seven to eight pairs of 

 convex'ging spicules, and in addition a few 

 at the base placed more or less horizontally. 

 In one series the third pair of converging 

 spicules in each double row is larger than 

 the rest, and projects beyond the polyp, 

 one of each paii' being larger than the other. 

 In the other there are no projecting 

 spicules. The polyp-spicules are spindles 

 and average 024 mm. in length and 002 

 mm. in breadth, while the projecting 

 spicules may reach a length of 0"5<i mm. 

 and a breadth of 006 mm. In the other 

 polyps the spicules vary from 016 to 024 

 nnn. in length and average about 0"016 mm. in breadth. 



The Stutzbundel is well developed, and consists of a number of large 

 spindles which may reach a length of IS mm. ; one or two may project 08 mm. 

 beyond the polyp. 



Cortical spicules : (a) In the stem there are long spindles, either straight 

 or curved, and having small simple spines on their surface, and often bifid at 

 one end. They vary in length from 0-4 to 1-6 mm. and in breadth from 0-048 

 to 096 mm. 



(b) In the stalk the spicules are spindles, three- and four-rayed forms, 

 irregularly branched rods or spindles, all with numerous [)rominent spines on 

 the surface. The spindles vary from 0-16 to 0-8 mm. in length and from 0-04 

 to Oil mm. in breadth. Several of the four-rayed forms have three of the rays 

 arranged tripod-like, while the fourth stands straight up from the junction of 

 the other three. 



Canal-wall spicules : {a) In the stem there are spindles and a few small, 

 flat, striated forms. The spindles are long, slender, with simple spines on the 

 surface, and measure from 016 to It) mm. in length and from 0032 to Oil mm. 

 in breadth. 



Fig. 47. D. varicolor. 



