198 The Colour-Physwology of the Higher Crustacea. 
probable that the appearance of the bright spectrum to the trichromic 
is very similar to that of a spectrum of feeble luminosity to the normal 
sighted, in which only three colours-—red, green, and violet—are seen. The 
defective difference perception which is found in these cases accounts for 
most of the facts. Both these cases are bordering on the tetrachromic, as 
the sodium flame appears to give rise to a distinct sensation. 
The Colour-Physiology of the Higher Crustacea, Part ILI. 
By FREDERICK KEEBLE, M.A., University College, Reading, and F. W. GAMBLE, 
D.Sc., Zoological Department, Victoria University, Manchester. 
(Communicated by Professor Sydney J. Hickson, F.R.S. Received February 8,— 
Read February 23, 1905.) 
(Abstract.) 
1. The chromatophores of Hippolyte and Crangon are multicellular 
structures. Their branches show differentiation into a firmer ectoplasm 
and a more fluid mobile endoplasm in which the pigment occurs. 
2. The formation of the pigments in the larval and_ post-larval 
chromatophores is described. 
3. In addition to pigments, fat, in the form of colourless globules, occurs 
in the chromatophores of Hippolyte. This fat lies in special cells of the 
chromatophore, and exhibits a mobility similar to that of the pigments of 
the chromatophore. 
4. If fed and kept in the dark, or if starved and kept in the light, Hippolyte 
loses little of its chromatophoric fat. Depletion of fat occurs, however, in 
starved, dark-kept, animals. These, when exposed to sunlight for five or six 
hours, show fat in their chromatophores. These results show that the 
colourless chromatophoric fat 1s a reserve food material, and point to the 
conclusion that in the accumulation of this reserve fat, light plays an 
important part. 
5, At the time of settling on the weeds of the sea-shore, Hippolyte varvans 
is a colourless or faintly brown-striped animal. At this stage it is extremely 
sensitive to the light conditions of its environment, assuming the colour 
of its surroundings within 24 hours. If the environment be changed, 
sympathetic change of colour takes place in three days. MHalf- and full- 
grown Hippolyte are less susceptible. With them sympathetic colour-change 
occupies a week or more. 

