263 



In preparations fixed with Osmic acid and mounted in glycerine 

 jelly the chromatophores show, in addition to red, orange and blue 

 pigments, the granular fat associated with, but distinct from, these 

 pigments. 



The fat in the form of spherical colourless granules .5 — 1 f.i in 

 diameter, lies either in the centres or in the branches of the chroma- 

 tophores. In a green Hippolyte, for example, the fat granules run in 

 rows which follow the lines of the branching and anastomosing chro- 

 matophores in which they occupy separate tracts. 



2) Movements of the Fat of the Chromatophores. Like 

 the pigments themselves, the fat of the chromatophores is mobile. At 

 night when the animals are in the nocturnal phase (Gamble and 

 Keeble, 1900) all pigments being contracted to the centres, the fat 

 is likewise aggregated in the centres. When the pigments pass into 

 their branches, at daybreak, the fat also passes into its branches. 

 When the pigments are fully expanded and occupy the finest inter- 

 cellular ramifications, the fat appears in the form of a fine net-work 

 — a lacteal system — about the terminations of the chromatophores 

 in skin, muscle and connected tissue. Though, broadly speaking, fat- 

 movement and pigment-movement correspond, the correspondence is 

 not absolute, nor does artificial stimulation always afi'ect pigment and 

 fat alike. 



3) The occurrence of fat in relation to food and to illu- 

 mination. Fed and starved Hippolytes show the same general pheno- 

 mena of fat distribution. The fat of the chromatophores appears, 

 however to be independent of the food supply. 



Light, on the other hand, exerts a powerful influence on the 

 occurrence of fat in the chromatophores. Thus, Hippolytes taken 

 from the sea and exposed for an hour to bright sunlight, shew a den- 

 ser network of finer mesh than do controls kept in difl'use light. 



Continued darkness produces, after five to eight days, depletion 

 of the chromatophoric fat in male and immature female specimens. 

 Depletion in mature females occurs in from eight to ten days; in large 

 Hippolyte viridis^ the process may even then be incomplete. 



Such dark-kept specimens and controls kept for the same length 

 of time in difi'used light, exposed for three hours to direct sunlight 

 showed dense networks of large colourless fat-granules in both cases. 



4) Summary. The Chromatophores of Jïijojoo/î/^e normally con- 

 tain colourless fat distributed in tracts separate from those occupied 

 by the red and yellow pigments. The fat exhibits movements very 

 similar to those of the diurnal pigments. These movements bring the 

 fat from the chromotophore- centres to the inter-cellular spaces of the 



