MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 585 



mesog^loea also becomes very thin, and the epithelium in some cases undergoes a glandular 

 moditication. 



The filaments are of the usual Madreporarian type, with the mesenterial endoderm swollen 

 behind (fig-. 143). Numerous long, narrow, nematocysts occur, and more rarely one of the large 

 oval form; supporting cells almost surround the hinder region, and diminish in length towards 

 the mesogheal axis. Granular cells, somewhat similar to those in the column wall and stomoda;um, 

 are found in the anterior portion of the filament. 



The swollen mesenterial endoderm immediately behind the filament is remarkable for the 

 abundance of large, pyriform, clear or almost clear, gland cells. Zooxanthella? are here absent, 

 except in the lower regions, and very few granular gland cells are seen. In most instances the 

 expanded region terminates gradually, passing into the ordinary endodeniial lining (figs. 143-14.5). 



Certain of the filaments become glandular in chai'acter throughout a part of their course, 

 having their cells either wholly or in part charged with a bright yellow, granular substance. A 

 similar glandular character may be assumed also by the swollen mesenterial endoderm immediately 

 behind the filament, no sharp line of separation distinguishing the two series (figs. 144, 145). 



The endoderm of the skeletotrophic tissue is a narrow epithelial layer in the upper region of 

 the polyps, and contains zooxanthelhe and clear gland cells, but in the lower region it undergoes 

 a great alteration. It gi'adually increases in thickness until it is enormously broad, and loses at 

 the same time most of the zooxanthelhi? and granular cells; the nuclei diminish in size and are 

 accumulated toward the free surface, and the whole tissue stains but little. The supporting 

 lamella is clearly distinguishable, and desmoidal processes occur practically throughout its 

 skeletal surface, though more pronounced along the line of attachment of the mesenteries. The 

 ectoderm or calicol)last layer is a uniform, thin epithelium in the regions of active growth, as at 

 the edges of the septa. The region around the insertion of the septa in the polypal wall also 

 appears to be one of active growth, the cytoplasm and large nuclei of the calicoblasts staining 

 deeply. 



The polyps are hermaphrodite; male and female elements may occur on the same mesentery 

 (fig. 14u), or on separate mesenteries (fig. 146). 



P'amily OCTJI^I>rir>>E:. 

 Genus OCULINA Milne Edwards and Haime." 



Polyps smooth, usually spirally arranged, raised obliquely from the surface of the colony, distant, 

 except toward the apex of the branches, form fixed arborescent colonies or tufts. Perithecal portion of 

 the gastro-coelomic cavity and mesenteries (edge-zone) greatly prolonged, may pass into "coenosarc." 

 Free portion of column cylindrical or somewhat conical, overfolding on retraction; no sphincter. 

 Tentacles hexamerous, tricyclic, entocoelic and exocoelic, minutely tuberculated and knobbed. Disk 

 circular, often prolonged in a conical manner. Stomodseal walls feebly ridged. 



Mesenteries hexamerous, dicyclic, six pairs complete, all filamentiferous, two pairs of directives. 

 Septal invaginations hexamerous, tricyclic, entocoelic and exocoelic, unite centrally (columella) in lower 

 region, and divide the gastro-coelomic cavity into twelve distinct loculi, each with two unpaired 

 mesenteries. 



Asexual reproduction by columnar gemmation at the apex of the branches; rarely by fissiparous 

 gemmation. 



Example. — Oculina diffusa Lamarck. 



" "Colony arborescent or in tufts, torallites arranged more or less distinctly in ascending spiral series, or scattered 

 irregularly, prominent or sunken, often arising from an incrusting base. Cceiienchynia solid and smooth or tinely 

 papillose. Calices circular, oval, prominent or depressed. The columella either well developed and papillary at 

 the surface, compact at the base, or rudimentary. The septa are well developed, entire or slightly spinulose where 

 free, some exsert. Pali exist before all the septa except those of the last cycle. Costii' as striations, or decided 

 jirojections extending a short distance from the calicular margin. In rapidl>- growing forms there is no ccenenchyma 

 independent of the buds. Endotheca may exist." (Duncan, ISS.5, p. 41.) 



