Part II.—Stichodactyline and Zoanthee. 17] 
the disc, gland cells occur, and the endodermal muscle is much stronger than in 
the tentacles. 
The stomodeum is greatly folded in all the sections, the ectoderm being 
followed by long, narrow or broad processes of mesoglea. The first layer is 
densely crowded with large, granular gland cells extending completely across, 
but stinging cells are rare. A very delicate nerve layer can be discerned, and 
the merest trace of ectodermal and endodermal musculatures. Zooxanthelle are 
scarce in the endoderm, but gland cells are numerous. 
The gonidial grooves are interesting in the amount of histological detail 
indicated, and remarkable for the enormously exaggerated endoderm (PI. x1v., fig. 2). 
The ordinary stomodzal ectoderm and mesogloea narrow just before reaching the 
groove, and then all the three layers become much thickened, the endoderm most 
so. In the ectoderm, the nuclei are nearly all restricted to a narrow, extremely 
well-defined zone, a little below the ciliated margin; for a short distance within 
this zone the layer is almost clear, and then another nucleated zone is apparent, 
but in this case the nuclei are much fewer and do not stain so deeply. Then 
comes another clear zone, and afterwards a nervous layer from which fibrillee 
extend to a very feeble muscle layer, apposed to the inner face of the mesogleea. 
Ganglionic cells are scattered here and there among the fibrille. The whole 
succession of details can be easily traced all round the gonidial ectoderm. ‘The 
mesogloea is smooth on its ectodermal aspect, but the endodermal aspect is 
irregular ; it is finely fibrous in structure, and many isolated cells are included. 
The endoderm of the groove is enormously swollen, and of peculiar structure. 
Nearly all the nuclei and protoplasmic contents are aggregated towards its 
periphery, the greater portion of the layer appearing highly reticular in section ; 
granular gland cells are scattered about, more numerous towards both its internal 
and external limitations. ‘The mesogloea of the directive mesenteries as it passes 
through the endoderm is extremely narrow. 
Several specimens dissected transversely exhibit numerous pairs of mesenteries, 
arranged in four orders. The number is very variable, no two of the examples 
being alike. Two gonidial grooves and two pairs of directives were, however, 
present in each case. To the naked eye both sides of the groove are smooth, 
and readily distinguished from the rest of the stomodzum by being unfolded ; 
the mesogloea and endoderm are also much thickened. T'welve pairs of perfect 
mesenteries were present in a transverse dissection through the middle stomodzal 
region of a rather small polyp, and also second and third imperfect cycles. In 
places these exhibited the normal regularity, but in some of the exocceles additional 
imperfect pairs belonging to lower cycles occurred, and all stages in the develop- 
ment of new pairs could be traced. In another polyp between thirty and forty pairs 
of perfect mesenteries were counted in sections through the middle stomodezeal region, 
