Nervous System of Actinia. 269 



and becomes superficial ; moreover the granules then contribute to the 

 colour of the chromatophore, and probably they always do so to a certain 

 degree. 



The refractile cells are not invariably confined to the layer above the 

 so-called cones of Eotteken, although they are often thus limited in their 

 position, especially if there are bacilli covering them. In parts of the 

 same chromatophore, where this apparently normal arrangement is seen, 

 and especially on the microscopic chromatophores between the larger 

 kinds, the large refractile spherules are found between and in the midst 

 of groups of the cones (PI. II. fig. 16). 



In the chromatophores there is considerable variety in the size of the 

 refractile cells ; they appear to be developed from the small cells with 

 a circular outline, which contain a few dark granules, and which are 

 found in considerable abundance amidst the enveloping granular tissue 

 (PI. II. fig. 8). 



The most striking of all the histological elements of the chromato- 

 phores are the cones of E-otteken, or the nernatocysts with imperfectly 

 visible threads of Homard. They are divisible into three series : 



a. Elongated simple cells, cylindrical in shape, with rounded and 

 somewhat pointed extremities, consisting of a tough cell-wall which is 

 capable of being bent without being broken or ruptured, and of colour- 

 less transparent contents which are rather viscid (PI. II. fig. 5). They 

 are four or five times the length of the bacilli, and three times their 

 width. The cell- wail is faintly tinted with the peculiar colour of the 

 chromatophore. These elongated cells are not conical, nor can they be 

 really termed cones with any propriety ; when observed through their 

 greatest length, or when the light traverses their long axis, the cell-wall 

 appears dark and the centre very refractile. They exist in vast multitudes 

 over most parts of the chromatophore, and also in the intermediate tissue 

 and its microscopic chromatophores. 



/3. Cells of the same shape as " a," but the cell-wall is faintly striated, 

 the appearance being very distinct under a power of 2000 diameters 

 (PI. II. fig. 6). These cells are very numerous, and were noticed by 

 Eotteken ; they appear in the same position, and often amongst the cells 

 with simple walls. 



y. Cells of the same shape and size as " a and /3," with a well-deve- 

 loped thread within them, which usually has no barb (PI. II. fig. 7). 



These cells are common where there are no bacilli, but they occur here 

 and there in all parts of the chromatophore circle. 



In some rare instances the " Eotteken bodies" (for thus I would name 

 these remarkable cells) are closely approximated, side by side, without the 

 intervention of any structure ; but, usually, there is a very thin layer of 

 granular protoplasm, containing small cells, between them. 



As the bodies are cylindrical and more or less closely applied by their 



