50 



The colon)' is distinctly divaricate, bush-shaped, flattened in one plane and 

 of an irregular oval outline, the long axis of which stands at an angle to that 

 of the stalk. 



The stalk is long, measuring in the larger specimen 4 cm. and in the 



smaller 3'3 cm. It is slender and flabby, 

 delicate in appearance and with a finely 

 granular surface. 



The polyparium is irregularly oval in 

 outline and consists of several branches of 

 unequal length. In the larger specimen the 

 main stem divides into three prominent por- 

 tions just above the origin of the lower 

 flattened branches. Each of these main por- 

 tions gives off" a number of smaller branches 

 which give rise to the polyp-bearing twigs. 

 In the smaller specimen the stem rises a little 

 above the origin of the flattened branches and 

 then divides into two main portions which 

 give off" branches as in the larger specimen. 

 The branches arise from the main portions 

 at an acute angle. In the larger specimen 

 the lower branches, two in number, are 

 flattened, leaf-like structures which almost 

 surround the stem leaving only two small free spaces, and being reflexed sur- 

 round the top of the stalk, in collar-like fashion. Directly below each of the 

 free spaces a small ordinary branch arises. In the smaller specimen the lower 

 branches are more or less flattened but do not form a collar. 



The polyps are arranged in small diverging groups of six to ten, and are 

 placed at an obtuse angle on stalks which measure on an average about 2 mm. 

 in length, although many of the younger polyps have shorter stalks. They 

 are cylindrical and form a sort of double cone with the wide basal portion 

 forming the middle line of the polyp length, and the oral cone tapering more 

 gradually than the basal one. They measure on an average 054 mm. in height 

 and ()■<) mm. in breadth. The polyp-spicules are arranged in the following 

 manner : At the base there are eight double rows in each of which there are 

 two to three pairs of spicules meeting at an angle which varies from acute to 

 obtuse but is usually obtuse ; above this there is a horizontal ring of curved 

 spicules two deep, and finally rising above this, in line with the eight double rows 

 below, there are eight points each of which has one pair of spicules which 

 meet at a very acute angle. Of the latter one is much larger than the other 

 and may project for a considerable distance beyond the polyp. Alongside and 



Fig. 26. D. mirabilis. 



