269 



Spicules. 



The great majority of the spicules are arranged irregularly so as to 

 form a dense feltwork on the surface of the canals giving consistency 

 and rigidity to the whole colony, but many are also embedded in the 

 mesogloea. On several parts of the colony, however, the arrangement 

 is particularly regular, e. g. on the expanded disc of the verruca (fig. 5), 

 on the protective prolongations of the wall of the anthocodia (fig. 9), 

 and also on the tentacles, where, in all cases the arrangement is biserial. 



All are irregularly echinate, while many may be called warty. The 

 spines vary greatly in form and size, some sharp and triangular stand- 

 ing at right angles to the sjsicules. others hooked and thornlike, while 

 others are truncated. They are, for the most part, simple, but com- 

 pounds forms are not infrequent. No type, however, can be said to be 

 characteristic of any particular part of the colony. 



The spicules consist chiefly of straight and curved spiny spindles, 

 some approaching the "scaphoid" form so characteristic of the genus 

 Gorgonia, thus showing convergence in another direction. Other forms 



Fiff. 15. 



aoc 



Fig. 14. Spicule enlarged (x390) to show the organic axis, ax, organic axis; br, 



branches of the axis. 

 Fig. 15. Transparent spicules of the outer wall of the trunk. 



are single clubs and clubs with a curved termination resembling "hockey- 

 clubs". 



In the decalcified sections an organic residue was to be seen in the 

 spicule cavities in the mesogloea, and an examination of the smaller and 

 more transparent spicules showed that there was an organic axis with 

 branches which passed out into the spiny projections (fig. 14 ax, organic 

 axis; òr, branches of the axis). 



It is interesting to note that the same has been recorded by Bourne 

 for Lemnalia, the genus most closely related to our form. 



The following measurements of spicules were taken : 



a. Transparent spicules of the outer wall of the trunk (fig. 15). 

 Straight spindles 0,85 X 0,03 mm; 0,75 X 0,04 mm. 

 Curved spindles 0,7 X 0,025 mm; 0,75 X 0,03 mm. 



