PLATE VI 



ASTRANGIA SOLITARIA Lesueur. 



Fig. 47. — Transverse section of a polyp through the stomodaeal region. The mesenterial notation is given in fig. 8e, 

 p. 462. At this level some of the mesenteries stretch in undivided continuity from the column wall to the 

 stomodajuin, only sections of the exsert septa being represented; others are already separated into 

 calicular and pericalicular parts by the upgrowth of the thecal wall. X 50. 



CLADOCORA ARBUSCULA (Lesueur). 



Fig. 48. — Portion of a colony constituted of two subcolonies, one having three united polyps and the other two. 



Fig. 49. — Transverse section through the stomodeeal region of a polyp, presenting the relationships of the mesenteries 

 and septal invaginations. The perithecal part of the polyp is not represented. (See also p. 458.) X 50. 



Fig. 50. — Transverse section of a retracted tentacle, showing the distribution of the nematocysts in isolated projecting 

 batteries. X 300. 



Fig. 51. — Transverse section of a portion of a polyp through the lowermost part of the stomodneal region. The 

 stoiiiudii-al ectoderm is reflected along each of the three mesenteries still connected with the stomodseum. 

 The pair of directive mesenteries to the right are now altogether free, but each is capped by a tissue 

 exactly like that lining the stornodamm. Mesenterial filaments are already developed on the incomplete 

 mesenteries, which never reach the stomodieum. The perithecal parts of the mesenteries do not 

 exactly correspond in number with the intercalicular mesenteries, those of the younger members not 

 having yet reached so far. X 50. 



Fig. 52. — a, Transverse section through a portion of the column wall. The ectoderm comprises mostly large gland 

 cells, and the endoderm contains many zooxanthelhe. b, Transverse section through a part of the lower 

 stomodseal region. The ectoderm is constituted mainly of ciliated supporting cells and granular gland 

 cells, those in the deeper parts of the layer differing from the more peripheral. X 320. 

 610 



