84 



incandescent lamp into the jars which were otherwise 

 quite opaque. 



The effects of direct sunlight, reflected light and 

 scattered light upon the colour of Hippolyte were tested 

 hy exposing carefully recorded specimens to these in- 

 fluences in the open grassy space outside the Laboratory. 

 To prevent a rise of temperature in the sea-water, we 

 employed a circulation of water derived from the supply 

 in the Laboratory to flow through our observation-dishes. 

 The methods we used for investigating the effects of 

 rise and fall of temperature, electrical stimulus and of 

 toxic agents do not call for remark here. At night and 

 often during the day the records (chiefly microscopical) 

 were made by the light of an incandescent lamp. 



We have arrived at the conclusion that there are two 

 colour-phases in Hippolyte varians ; one diurnal, the 

 other nocturnal. The recurrence of these phases is to 

 some extent independent of the conditions of illumination, 

 although the colour itself may be profoundly influenced 

 by varying the quality and intensity of the incident light, 

 and also by other stimuli, which do not act through the 

 eye. 



The advantages which the Piel Laboratory affords for 

 work of this kind are very considerable, and while express- 

 ing our thanks to Professor Herdman and to the Curator 

 of the Laboratory (Mr. Andrew Scott), we wish to 

 acknowledge our marked indebtedness to the Lancashire 

 Sea-Fisheries Committee for the generous help which is 

 afforded by them for the prosecution of scientific work, 

 generosity which will surely become more widely 

 appreciated as it becomes more generally known. 



