692 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxt. 



tition into two nearly equal chambers which are roughly half-moon 

 shaped in section. This septum is not perforated, but the walls of the 

 chambers which constitute the inner wall of the stem are marked by 

 rather regularly distributed linear to ovate openings, the longest 

 diameter of which is transverse to the long axis of the stem. These 

 openings, on account of their function, may be called stomata. 

 (Plate LXXXV, fig. 3.) 



In other sections still nearer the proximal end of the stem it is seen 

 that the membrane dividing the stem cavity into two chambers is 

 really double, the two layers being divaricated at the ends of the par- 

 tition, the spacer thus bounded by the split ends of the partition and 

 the portion of the inner wall of the stem between them being the much- 

 reduced right and left axial chambers. 



A section taken across the rachis above the termination of the axis 

 shows that the chambers are all much reduced in size, the partitions 

 between them being thickened into fleshy masses of considerable 

 consistence. 



The canals entirely disappear near the end of the rachis, which ter- 

 minates in a little rounded knob covered at its extremity with a mass 

 of needle-like spicules. 



THE LEAVES. 



There are about nine pairs of rudimentary leaves below the first pair 

 with developed polyps. The lowest of these is extremel}'^ minute and 

 placed on a level with the lowest of the zooids on the dorso-lateral 

 aspect of the rachis. They are edged with a single row of rounded 

 papillae, which are, in fact, rudimentary calyces. 



The smallest papillge are on the inner and the largest on the outer 

 ends of the leaves. At the outer end there is a tendency toward a 

 zigzag arrangement of these papillaB, indicating the incipiency of the 

 formation of two rows. 



In the second pair this tendency is still more marked, there being 

 two rather well-defined rows of papillae extending nearly to the inner 

 ends of the leaves, and at about the sixth pair the rows extend the 

 entire length of the leaf border. 



The third leaf has three rows of papillae on its outer side, and these 

 grow more and more complete in successive leaves until on the eighth 

 leaf they extend along the entire border. 



The bimucronation of the calyces appears on the outer part of the 

 seventh leaf, while the tentacles of the polyps appear first on the outer 

 polyps of the ninth pair of leaves. Here the polyps are rosette- 

 shaped, when viewed from above, while on the tenth pair fully devel- 

 oped polyps with normal tentacles are seen. 



This pair can thus be considered the first pair of functional leaves. 

 There are about 30 polyps to the row, and the leaf is narrow and 

 scalpelliform. 



