ACTINIARIA 



179 



ing cells (PI. 4 fig. 9), here and there a granulous gland cell was observed; on 

 the other hand, there were no nematocysts, excepting in the rim of the spots, 

 where they are, however, very rare. In the other part of the columnar ectoderm, 

 the nematocysts, as well as the gland cells, were numerous. Of the gland cells some, 

 the fewer, were more homogeneous, the others, the more numerous, contained a 

 multitude of small brownish granulae. Whether the latter, which often reach a 

 considerable size, are gland-cells of the same kind as the former, but in a differ- 

 ent state of secretion, I cannot with certainty decide. Possibly the circumstance 

 that I have not observed any such in the unpigmented specimens, speaks in 

 favour of this suggestion, though I hardly believe tliis to be the case. In the 

 unpigmented specimens the homogeneous gland-ceUs were, however, numerous, 

 but the ectoderm of these specimens was not as well preserved as in the 

 specimens with spots. As above mentioned, there were in some specimens frag- 

 ments of a cuticle which is evidently easily deciduous. The cuticle seems to be 

 very thick but incompact and cracked, and not of typical appearance. The me- 

 sogloea of the column is thick and contains rather sparse protoplasma-poor 

 cells. The endodermal circular muscles are ver>' well developed and form high, 

 delicate, ramificated folds; in the region of the sphincter the muscle layer is 

 weaker. The sphincter is strong and of a somewhat variable type. In a specimen it 

 was on transverse sections round and distinctly palmate without a main lamella, 

 and with a tendency (on some sections) to form meshes, in two other specimens 

 it was compressed and of variable structure in different sections of the same spec- 

 imen, now there was no distinct main lamella but rather several longitudinal la- 

 mellae in the middle of the sphincter, now these latter were fusing in the middle 

 part, or finally the sphincter was almost palmate. If a main lamella was pres- 

 ent, it was always more weakly developed at the base than in the middle part 

 (textfig. 179 from the specimen with spots). The ectoderm of the tentacles was 

 very high with numerous nematocysts 24 — 30 X 2 (2,5) n and numerous spiro- 



Cysts, 19 X I /i to 34 X 2,5 n in size. The longitudinal muscles of the tentacles Transverse section of sphincter 

 ■' ^ ' '^^ ' ^ (fig. 179) and of part of a ten- 



(textfig. 180 transverse section of a part of tentacle from Michael Sars- tacle (fig. 180). 



Exp. St. 10) were ectodermal with rather high folds, in transverse sections often of a palisade-shaped appear- 

 ance. In the apex the folds were often a little branched. The structure of the radial muscles in the oral disc is 

 the same as that of the longitudinal muscles of the tentacles ; the folds were, however, lower here, and so was 

 the ectoderm. The ectoderm of the actinopharynx was, in the ridges, very high and contained very closely 

 packed nematocysts, (26)29 — 36x3 — 3,5 /t in size, in the furrows considerably lower and with sparser nema- 

 tocysts. The size of the nematocysts and spirocysts in four specimens was as follows (p. 181). 



The pairs of mesenteries were in 5 examined specimens 24 (6 + 6 -f- 12). The mesenteries of the third 

 cycle showed the same differentiation as in E. marsufialis, in as much as half the pairs had reproductive 



2»* 



Fig. 180 



Textfigs. 179 — 180. 

 Epiactis arctica. 



