HIPPOLYTE VARIANS. 611 



half a millimetre in length, and delicately plumose. The 

 commonest form, perhaps, is that of an irregular blue net- 

 work somev/hat elliptical in outline (PI. 35, figs. 22, 25). 

 The marginal strands of the network fray out into thinner, 

 lighter coloured processes ; the central strands are thick, and 

 enclose in their meshes a ti*ansparent substance. By reflected 

 light the blue spots are pale opaque blue, by transmitted light 

 nearly black. 



A remarkable feature of these blue spots is that they 

 are very generally separated, optically at least, from the 

 surrounding chromatophoric network by a clear enclosing 

 space. Not entirely, however, for across this clear halo there 

 extend fine greenish-yellow or bluish radiations, continuous on 

 the one hand with the frayed-out marginal strands just re- 

 ferred to, and on the other with the surrounding " chromato- 

 phores," Usually two or more of these radiations are stouter 

 than the rest and more obviously continuous with the ad- 

 jacent network.^ They differ, too, not only in being stouter, 

 but also in the character of the pigment which they contain ; 

 for by day they contain red pigment and join the red net- 

 work we have described, whereas at night they contain blue 

 pigment. We refer to this matter, which belongs to the 

 next section, for the purpose of showing that the red pigment 

 must either be concealed by the thick blue granular pigment 

 at the centre of the " blue spots," or that the blue must be 

 replaced by red radiations formed out of this pigment. 



We will now briefly discuss the green and pink colour 

 forms. Specimens emerald green to the eye, examined by 

 light transmitted through an Abbe condenser, appear much 

 paler and yellower in colour; while by reflected light the 

 green assumes a dull dark tone. The body of the prawn is 

 transparent enough to allow the spherical, clearly defined, 

 almost black centres of the " chromatophores,'^ and the deli- 

 cate close yellow network formed by their processes, to be 

 clearly seen. The black centres have a faint bluish or green- 

 ish halo, and under the high power a delicate blue reticulum 



» PI. 35, fig. 25. 



