33 



a number of smaller branches are given off. Immediately above this the stem 

 gives off three main branches, one of w^hich rises partly from the upper surface 

 of one of the lower Hattened branches ; then it continues straight upwards for 

 a considerable distance giving off only a short thick branch at one side. All 

 the princii)al branches are thick and cylindrical in shape and give off from their 

 surface a number of smaller branches, which directly, or by one or two divisions, 

 give rise to the polyp-bearing twigs. The lower branches are flattened leaf- 

 like structures which surround the stem, forming a sort of collar and hiding 

 the upper part of the stalk. Two of them almost completely surround the 

 stem, leaving only two small free spaces, and have their edges much convoluted, 

 the free lateral surfaces curling upward towards the apex of the colony, thus 

 forming a sort of triangular space over the free spaces. In these free spaces 

 at a slightly lower level two smaller branches arise with cylindrical stalk and 

 flattened upper portion which corresponds to the triangular space and is spread 

 out in umbrella-like fashion. 



The polyps are arranged, somewhat loosely, in small bundles of three to 

 eight ; the divergence of the polyps of a bundle is seen more markedly on the 

 lower part of the polyparium. From the edge and from the upper surface 

 of the flattened lower branches the polyps arise singly, or in small groups from 

 twigs. The heads are small, measuring 0-54 mm. in height by 048 mm. in 

 average breadth, and are placed on stalks of about 2 mm. in length at an angle 

 which is usually obtuse. The spicules are arranged in eight double rows, in 

 each of which there are five pairs of converging spicules ; the uppermost pair are 

 much longer than the others, run almost parallel, and project beyond the polyp- 

 head. The lower spicules measure on an avei'age 018 mm. in length, wliile the 

 upper have an average length of 0'36 mm. and project 018 mm. On some of 

 the younger polyps the difference between the upper and lower polyp-spicules is 

 not so marked and the projection is not so apparent. On the aboral surface of 

 the tentacles there are two rows of almost transversely placed, flat, toothed 

 spicules which are thickly crowded together. 



The Stutzbundel is well developed, one of the spicules may reach a length 

 of I'o mm. and project for a distance of 0-36 mm. ; usually the tip of a second, 

 and sometimes that of a third, may be seen projecting. Various stages in 

 development can be seen, from cases where the .Stiitzbiindel is represented 

 by a slightly larger sjjicule up to the complete form. 



Cortical spicules : {a) The spicules of the stem and main branches are 

 placed transversely, those of the smaller branches and twigs obliquely trans- 

 versely or longitudinally. They are large spindles, straight or curved, and 

 thickly covered with regularly arranged blunt to roughish spines. Several show 

 bifurcation at the end. They vary in length from 0-33 to 34 mm. and in 



breadth from 006 to 024 mm. 

 5 



