Anatomy of Gorgonid^. ioi 



of the tentacles is covered with epitheHal cells bearing cilia. 

 These latter are ditBcult to observe even in a living specimen, 

 but their presence was proved b)^ the rapid motion of particles 

 in the water near the surface of the tentacles as well as by 

 the fact that individual epithelial cells when detached, rotated 

 and gyrated much as do ciliated epithelial cells from the mouth 

 of a frog or trachea of a dog. 



A transverse section of a tentacle (PI. I, ftg. 8,) reveals the 

 fact that it is tubular in structure being lined with colum- 

 nar endodermal cells much like those lining the gullet cavity 

 of the polyp, although the latter is ectodermal in origin. The 

 covering of ectodermal cells is well shown in the figure, as well 

 as the less compactly aggregated mesodermal cells (c). Three 

 papillcC are also shown in longitudinal section. The papillge 

 do not appear to contain central prolongations of the tentacular 

 cavity but se-^m to be mere projections of mesoderm covered 

 with ectoderm. 



A single papilla, when examined in a fresh specimen under 

 a 1 objective, presents the appearance shown in fig. 4. The 

 ectodermal cells are well differentiated and appear clear and 

 somewhat quadrate in form. The mesodermal cells (b) on 

 the contrar}^, are perfectly spherical and filled with a pigment 

 which gives the brown color to the pol3-p. Fig. 5 shows one 

 of these mesodermal cells much enlarged. These cells seem 

 very loosely aggregated and act much as the cells of the 

 hydra when pressed between the slide and cover, showing a 

 tendenc}' to separate upon the application of ver\' little pres- 

 sure. 



The mesenterial -filaments (PI. I, iig. 6, d) are long convo- 

 luted thread-like structures that hang from the lower end of 

 the gullet, near where the mesenteries are attached. They 

 seem to be free inferiorl}', and are said to be concerned in 

 some way with digestion.' 



I. "The secretions of the coiled and twisted filaments (mesenterial fila- 

 ments) at the edge of the mesenti^ries must be regarded as aiding indigestion." 

 Zoology. Claus and Sedgwick, p. 224. 



