PENNATTJLIDA DREDGED BY H.M.S. "TRITON." 151 



Plate XXI. 



Fig. 1. — Virgularia tuherculata ; ventral surface, x 3. 



Fig. 2. — Virgularia tuherculata; portion of racbis, ventral surface, showing arrangement of 

 polyps in groups of threes ; also the tubercular calyx processes and the varying 

 conditions of the calyx during retraction of the polyp, x 17. 



Fig. 3. — Virgularia tuherculata ; two spermatospheres from lower part of racbis of the speci- 

 men shown in fig. 1. x 70. 



Fig. 4. — Pennatula phosphorea var. aculeata; from right side. Shows characteristic shape of 

 leaves, also both small and large zooids. x 2. 



Fig. 5. — Pennatula phosphorea var. aculeata ; transverse section of racbis with one entire leaf 

 and the base of the corresponding one of the other side. Shows shape of leaf ; 

 shape and arrangement of zooids both large and small ; great thickness of wall of 

 rachis, and small size of its main canals, x 4. 



Fig. 6. — Pennatula phosphorea ; transverse section of rachis with entire leaf of normal form, for 

 comparison with fig. 5. Shows great width of leaf, absence of large zooids, thinness 

 of walls of rachis, and large size of main canals, x 4. 



Fig. 7. — Pennatula phosphorea var. aculeata ; lower end of rachis from left side. Shows stages 

 in development of polyps, and especially the simultaneous appearance of the 

 calyx processes and of the tentacles ; also the primitive independence of the 

 polyps of one another. X 17. 



Plate XXII. 



Illustrating the anatomy of the large ventral zooids of Pennatula phosphorea var. aculeata. 



The reference letter t l in the figures on this plate should be l\ 



Fig. 8. — Longitudinal section of large ventral ?,ooid and of the part of the rachis from which 



it arises. Shows structure of large zooid and of one of the small zooids. x 50. 

 Fig. 9. — Transverse section of a calyx process of a polyp, for comparison with the succeeding 



figure, x 150. 

 Figs. 10 to 16. — Transverse sections through one of the large ventral zooids at various parts of 



its height, fig. 10 being close to the apex and fig. 16 at the base of attachment to 



the rachis. x 150. 

 Fig. 10. — Through upper end of zooid, showing one calycular cavity. 

 Fig. 11. — Lower down ; shows two calycular cavities. 

 Fig. 12. — Lower down still ; shows three calycular cavities. 

 Fig. 13. — Through upper part of mouth ; shows long cilia of siphonoglyphe. 

 Fig. 14. — Through lower part of mouth ; shows five calycular cavities. 

 Fig. 15. — Through stomodpeum about the middle of its length. Shows eight septa and septal 



chambers. 

 Fig. 16. — Through lower part of polyp cavity, showing the two mesenterial filaments, and the 



remains of the other six septa. 



Plate XXIII. 



Fig. 17. — Diihenia abyssicola var. smaragdina. Ventral surface, x 3. 



Fig. 18. — Dubenia abyssicola var. smaragdina. Portion of rachis from left side. Shows 



arrangement of polyps in pairs, each pair embraced at base by a fan-shaped spicular 



plate, x 17. 

 VOL. XXXII. PART I. 2 B 



