72 On the Nervous System of Actinia. 



parts of the same chromatophore, where this apparently normal 

 arrangement is seen, and especially on the microscopic chromato- 

 phores between the larger kinds, the large refractile spherules 

 are found between and in the midst of groups of the cones 

 (PI. LXIX, 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. LXIX., Fig. 8). 



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

 tophores are the cones of Kotteken, or the nematocysts with imper- 

 fectly 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 

 colourless transparent contents which are rather viscid (PI. LXIX., 

 Fig. 5). They are four or five times the length of the bacilli, and 

 three times their width. The cell-wall 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. 



^. 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. LXIX., Fig. 6). These cells are very numerous, and 

 were noticed by Rdtteken ; they appear in the same position, and 

 often amongst the cells with simple walls. 



7. Cells of the same shape and size as " a and /9," with a well- 

 developed thread within them, which usually has no barb (PI. LXIX., 

 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 sides, there is more space between them in some places than 

 in others ; and it is in these spots, where the bodies cannot come 

 in direct contact, that their intermediate structures are elongated 



