70 0)1 the Nervous System of Actinia. 



them were examined in a large specimen of a living pale-green 

 variety of Actinia mesemhrijantliemum from the Mediterranean. 

 8. The tissues of the chromatophores of the Actinia mesemhryan- 

 themum were again examined with a view to explain the differences 

 between M. Eotteken's and my own results. 



The rounded, free, coloured, external layer of a chromatophore 

 ■was carefully disengaged from the granular tissue beneath it, so 

 that the baciUi of Kotteken, the refractile corpuscles, and his so- 

 called cones were separated from the rest. This turquoise-coloured 

 film was floated and carefully placed on a iilass slide, the bacillary 

 layer being inferior and on the glass, whilst the proximal ends of 

 the cones were free in the water. No thin glass was placed over 

 the film, and an object-glass of -^-inch focus was used. The appear- 

 ance presented under this low power (by transmitted light) was 

 very remarkable, for a great number of brilliant points of light 

 were seen surrounded and separated by dark opaque tissue. "When 

 a ^-inch object-glass was used, the appearance was less striking, for 

 the points of light were more diff'used. No trace of an object could 

 be seen through the refractile tissues. 



The transparent and retractile tissues were the so-called bacilli, 

 the globular bodies and the " cones " already noticed ; and the tissue, 

 which was impermeable by light, consisted of the colouring matter 

 in small dull granules, cells small and round in outline and granular, 

 and also the cell- walls of the cones. 



Sections through a chromatophore were made at right angles to 

 the point of the greatest convexity of the surface, and thin slices 

 were floated off carefully from the line of section on to glass shdes. 

 The shces included (a) the coloured outside of the chromatophore, 

 (h) the tissue beneath it, and (c) some muscular fibres which limit 

 the endothelium. Sea-water was used as the medium, and a thin 

 glass cover was applied after the specimens had been examined with 

 a low power. 



Externally was the bacillary layer (PI. LXIX,, Fig. 15). Eotteken 

 describes this as a cuticular layer broken up into bacilli by numer- 

 ous pore-canals. Examined, however, in the fresh subject, this 

 external layer consisted of a vast multitude of small rod-shaped 

 bodies, sharply rounded but conical at both ends, very transparent, 

 and resembling the smallest nematocysts of the tentacles without the 

 internal thread (PI. LXIX., Fig. 2). These are placed side by side, 

 and the external rounded end of each is sepiarated by a small space 

 from the terminations of its neighbours. These ends are free and 

 are in contact with the water in which the Actinia lives. The rods 

 are cylinders, and are separated from each other by a very delicate 

 film of protoplasm, in which are numerous dark opaque granules and 

 a few flat simple colourless rounded cells (PI. LXIX., Fig. IJ). The 

 inner ends are shaped like the external, and arc imbedded in the 



