1902.] 



The Golour-phyniology of Hiyher Crustacea. 



69 



" The Colour-physiology of Higher Crustacea." By Frederick 

 Keeble, M.A., Heading College, Heading, and F. W. Gamble, 

 D.Sc, Owens College, Manchester. Communicated by Pro- 

 fessor S. J. Hickson, F.E.S. Eeceived July 16, 1902. 



(Abstract.) 



The following statement is a condensed summary of the results of a 

 research into the form and physiology of the pigment-bearing organs 

 (chromatophores) of certain Schizopod and Decapod Crustacea with 

 especial reference to the effect of light on these organs and on these 

 animals. The evidence for the statement will appear in a full and 

 illustrated form in the " Philosophical Transactions." The Grant 

 Committee of the Eoyal Society allotted £25 for this research. 



A. The Influence of Light. 



L Under the influence of light the secretory activity of certain 

 organs is modified : an acid substance appears periodically in the 

 "liver" and muscle: the appearance and disappearance of acid sub- 

 stance in liver and muscle coincides broadly with nocturnal and diurnal 

 colour-change. 



2. In the progressive movements and orientations of the whole 

 animal called forth by light, background is the most important factor : 

 more powerful than change of light-intensity. By change of back- 

 ground, black to white, the direction of a light-induced movement 

 may be reversed. 



3. The response of the chromatophore-pigments to light is two-fold : 

 direct ; and indirect, through the mediation of the eye. The indirect 

 response alone leads to an enduring redistribution of pigment. 



4. The ultimate effect of monochromatic light on pigment-movement 

 is the same as that of white light. As with the latter, so with mono- 

 chromatic light, background — white (scattering), black (absorbing), 

 mirror (reflecting) — determines the nature and extent of the pigment- 

 movements. In describing an effect of light, that light must be con- 

 sidered in combination with its background. Neglect to do this must 

 lead to erroneous conclusions. 



5. " Beaction to background " is traceable to the eye, and is probably 

 a consequence of an asymetrical distribution of retinal pigment brought 

 about not by changes in the amount of light falling on the eye, so 

 much as by changes in the way in which light falls on the eye. 



B. The Bole of Pigments, 



6. The phenomena presented by the pigments are not exhaustively 

 explained by any " protective" hypothesis. 



VOL. LXXI. G 



