594 F. W. GAMBLE AND F. W. KEEBLE. 



It will be readily gathered from this historical sketch that 

 there has been no attempt to completely investigate in Hip- 

 polyte the different factors which in higher animals^ such 

 as the frog and chameleon, are known to be effective in pro- 

 ducing a change of colour. In the present paper we deal 

 with the effects of natural and artificial stimulation — both by 

 agents, such as light, working through the eye, and by others, 

 such as temperature, affecting the different parts of the body 

 equally — on the general colour and on the " chromatophores/' 

 The research, on which we are still engaged, was commenced 

 in the Owens College Zoological Eesearch Laboratory, and 

 was continued during the greater part of .1898 in the labora- 

 tory of the Lancashire Sea Fisheries Committee at Piel, near 

 Barrow. For permission to work in the laboratory we are 

 indebted to Prof. Herdman, and we beg to tender our hearty 

 thanks for the manner in which the resources of the labora- 

 tory have been placed at our disposal. During the present 

 year (1899) our investigations have been carried on, thanks 

 to the generous hospitality of M. E. Perrier, in the Labora- 

 toire Maritime de Tatihou, St. Vaast, Normandy. 



The problems of colour-change are so complex that this 

 research, which promised to be brief, has proved to be 

 well-nigh interminable ; at least we at present see no pro- 

 spect of the vein giving out. We therefore have decided 

 to give our chief results in order that we may be the freer 

 to pursue our investigations into some of those questions 

 mentioned in the text, to which these results have given 

 rise. We desire specially to draw attention to the section 

 dealing with " Nocturnal Colour,^' with " Periodicity of 

 Colour-change," and to the excellent coloured sketches of 

 Hippolyte on different weeds. These sketches, which we 

 owe to the skill and kindness of Miss D. Richardson, repre- 

 sent animals which had been allowed to make a choice as 

 to a place of anchorage among a variety of weeds. Even 

 the briefest examination will show how well in each case 

 Hippolyte avails itself of its opportunity. 



Our thanks are due to Professors Hickson and Weiss for 



