614 F. W. GAMBLE AND F. W. KEEBLE, 



confine ourselves to the consideration of liglit as a stimulus 

 to colour-change. 



Effect of Colour of Weeds on Colour-change in 

 Hippo! yte.^ — In this section and in the tables appended to 

 it we give some of the evidence we have obtained showing 

 that by replacing weed of one colour by that of another^ a 

 sympathetic colour-change may manifest itself in the prawns, 

 though this certainly takes place to a less marked degree 

 and more slowly than we had been led to anticipate. The 

 experiments were made either in our "air-circulator" vessels 

 or in dishes placed in the garden of the Piel Laboratory in 

 full light. The colours in the record are those of the prawns 

 as seen when placed, detached from their weeds, in a white 

 porcelain dish, proper precautions being taken to minimise 

 the ill effects of these artificial conditions. We deal here 

 only with the diurnal colours. 



In case the records of these experiments, which we feel 

 should be given at some length, are too tedious to be read 

 by those not engaged in colour work, we preface them with 

 the following summaiy. 



Adult prawns when placed with weed of a new colour (the 

 light intensity being as far as possible unaltered) are, under 

 the conditions of the laboratory, only capable of very slow 

 sympathetic colour-changes. Thus green Hippolyte placed 

 on brown weed conserve this green colour even for a week 

 or more, but in the end give way and become brown. Their 

 subsequent recovery when placed with green weed is more 

 rapid. We have repeated such experiments in the open, time 

 after time, and have found that the prawns were either quite 

 refractory or responded in this slow manner. 



Two greenish-brown, large female prawns are fully recorded 

 in Table III, p. 670. They were taken from a number captured 

 on July 26th, 1898, and were placed on the 28th in a glass jar 

 with Zoster a (green weed). A muslin cover was tied over 

 the jar, through which a strong current of water was main- 

 tained. From the table it will be seen that the animals re- 

 » See Tables I— IV, pp. 660—672, and Summary, p. 651. 



