Nervous System of Actinia. 267 



should be exercised on the thin glass, which is to be placed very carefully 

 and wet over the object. After the examination, carmine should be 

 added, or osinic-acid solution, 1 per cent, in strength ; but no results 

 can be relied on which are derived from the examination under the 

 influence of reagents alone, as they modify the natural appearance 

 greatly. 



So far as the chromatophores are concerned, my investigations took the 

 following course: -1. E/otteken's researches on the alcoholized Actinia 

 were followed in recent specimens. 2. The tissues of the chromato- 

 phores, of their margins, and of the spaces between them were examined 

 in a large specimen of a living pale-green variety of Actinia mesembryan- 

 themum from the Mediteranean. 3. The tissues of the chromatophores 

 of the Actinia mesembryantJiemum were again examined with a view to 

 explain the differences between M. Botteken'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 

 bacilli of Botteken, the refractile corpuscles, and his so-called cones 

 were separated from the rest. This turquoise-coloured film was floated 

 and carefully placed on a glass 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 

 J-inch focus was used. The appearance presented under this low power 

 (by transmitted light) was very remarkable, for a great number of bril- 

 liant points of light were seen surrounded and separated by dark opaque 

 tissue. When a J-inch object-glass was used, the appearance was less 

 striking, for the points of light were more diffused. No trace of an 

 object could be seen through the refractile tissues. 



The transparent and refractile 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 slides. The slices in- 

 cluded (a) the coloured outside of the chromatophore, (6) the tissue 

 beneath it, and (?) 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 baccillary layer (PI. II. fig. 15). Botteken de- 

 scribes this as a cuticular layer broken up into bacilli by numerous pore- 

 canals. Examined, however, in the fresh subject, this external layer con- 

 sisted of a vast multitude of small rod-shaped bodies, sharply rounded but 

 conical at both ends, very transparent, and resembling the smallest 



