The Actiniae of the Plate CoUection. 281 



The color of the columii in both specimeiis is dark chesnut 

 brown. the tubercles beiiig somewhat darker than the general sur- 

 face. In the npper part of the expanded individual the color is much 

 paler althongh the tubercles are as dark as they are below, and 

 the capitulum and tentacles are also paler while the stomatodaeum 

 again is dark. The color of the lower part of the scapns and of the 

 tubercles is largely due to the cuticle, while elsewhere it is due to 

 pigment granules in the ectoderm. 



Structure. The niesogloea of the column wall is thicker than 

 the ectoderm and is of an almost homogeneous or very finely fibrillar 

 structure. The tubercles are solid elevations of the niesogloea, ov^er 

 the summit of which the cuticle becomes greatly thickened, forming 

 on the larger tubercles a distinct conical boss. The circular muscles 

 are but moderately developed, their supporting processes being 

 slender and unbranched. A broad though thin mesogloeal sphincter 

 is present ; its upper edge is situated in the upper part of the capi- 

 tulum while the lower one is almost at the middle of the scapus, 

 its actual width being about 11.5 mm. In its upper part it oc- 

 cupies the entire thickness of the mesogloea, but in the scapus it is 

 thinuer and is separated from the ectoderm by a distinct band of 

 mesogloea. It is reticular in structure, without anj^ indications of 

 layering. 



The mesogloea of the tentacles is very thin and the longitudinal 

 muscles weak and entirely ectodermal. In the disc the mesogloea is 

 somewhat thicker than in the tentacles and the radial muscles are 

 also stronger and though still ectodermal show some anastomosing 

 of the branching processes. The ectoderm of the tentacles shows 

 an unusually large number of nematocysts. 



The mesenteries are arranged in three cycles and are on an 

 heptamerous plan. There are seven pairs of primary mesenteries, 

 seven secondaries and fourteen tertiaries. Of the primary mesen- 

 teries two pairs are directives, three pairs of perfect mesenteries 

 intervening between the two directives on one side and only two 

 on the other. Only the primary mesenteries are perfect and supplied 

 Avith well developed rauscle pennons, although both the other cycles 

 possess mesenterial filaments. The longitudinal muscles of the pri- 

 maries are fairly well developed (Fig. 71), occupying somewhat less 

 than one-third of the muscular portion of the mesentery, which, be- 

 tween the pennon and the well developed parieto-basilar, is very 

 thin. Acontia were present but no reproductive organs were seen. 



19- 



