74 



ERNEST WARREN. 



Apex of Main Stem (one Terminal Polyp) 



A perisarc is well developed, and the main stem is 

 annulated with four or five rings immediately above the 

 origin of the primary branches. At the base, where the 

 main stem arises from the hydrorhiza, there may be as 

 many as twenty rings. Occasionally an internodal group 

 of annulations may be found (fig. 2, /. a.). 



The lateral or primary branches are annulated at their 

 base, and also just in front of the origin of the secondary 

 branches or ramuli bearing the polyps. There is con- 

 siderable variation in the nature of the annulation; some- 

 times it consists of true rings, at other times it is a spiral 

 ridge running three, four, or five times around the stem, 

 and the spiral may be either a right-handed or a left-handed 

 one. The secondary branches bearing the polyps are annu- 

 lated towards their base. There can be little doubt that a 

 mechanical principle is involved in the presence of these 

 annulations, and that they strengthen the stem, for they 

 appear just in those places where there is most strain. 



The perisarc is of considerable thickness. It is nearly 

 black over the main steni and greater part of the primary 

 branches ; but it becomes pale brown toAvards the extremi- 



