i)3 MARINE BIOLOGY OF THE SUDANESE RED SEA. 



ou secondary branches and the twigs which spring from these. The secondary 

 In-anches are crowded closely on the primary and form catkins 1 5 to 2'5 cm. 

 in length, the larger catkins being of a compound character. 



In the cortex of the terminal polyp-bearing branches there is a longitudinal 

 arrangement of the spindle-shaped spicules, and this is continued on to tin- 

 dorsal surface of each polyp-stalk. 



The polyp-heads are bent sharply ou the polyp-stalks, so that the tentacular 

 surface faces the cortex of the terminal twigs. 



The cortical spicules of the stem and main branches form by interla(jing 

 a continuous armature. These spicules are of very diverse atd distinctive 

 forms, including the following : — 



(a) Boat-shaped spindles with few warts. 



(b) Carved spindles with long spines, which are more developed on the 



convex surface. 



(c) Very spinose club-like forms. 



(d) Triradiate spinose bodies. 

 {e) Irregular spinose bodies. 



The follow-r.ff measurements wei-e taken of length and breadth in uiilH- 

 metres : — 



(a) Boat-shaped spindles : 0-8 x 0-15; Owox 0-075; 0-67 x 01; 0-62 X 



0-1 ; 0-5 X 0-075; 0-45x0-09. 

 (h) Curved spindles : 0-95x0-15: 0-85 x 0-12; 0-8x0-15; 0-73x0-15; 



0-7 X 0-1 ; 0-65 x 0-15 ; 0-52 x 0-13 : 0-5 x O'l. 

 (c) Club-like forms : 33x0-25. 



The spicules of the polyp-head and polyp- stalk include long curved or 

 sinuous spindles with knob-like warts which in some cases are more numerous 

 and better developed at the tips of the spindles ; also spindles with only a 

 few poorly developed spines. 



The following measurements were taken of length and breadth in milli- 

 metres : — 



(1) Spinose spindles: 1-5x0-1 : 1-15x0-1; 1-1x0-12; 0-6x005: 



0-4x005; 0-2x0-02. 



(2) Smooth spindles with only a few spines: 1-2x0-09; 0-9x0-05; 



0-69x005. 



The spicules of the canal walls consist of spindles similar to those of the 

 cortex, but the form with few spines predominates. 



The following measurements were taken of length aud breadth in milli' 

 metres : — 



(1) Spinose spindles : 0-87x0-12; 0-85x0-12; 0-83 X 0-12 ; 0-6x0-1 ; 

 0-55x0-13; 0-5 X 0-1. 



[58] 



