HIPPOLYTE VAEIANS. 615 



mained during the first three days of an olive- green colour, 

 but became more transparent. It was only at midday on 

 the SUthj after having been for about fourteen hours in 

 the dark, that a distinct green colour manifested itself. 

 This green colour persisted in the light, and changed on the 

 31st to a greenish yellow, matching the lower parts of the 

 Zostera stalks. 



The change in this case from olive-green to bright emerald 

 green, accompanied by an enhanced transparency, is not 

 very great j but the close agreement of the colour with that 

 of the weed is striking. 



We have also other records of brown prawns becoming 

 green on green weeds. Thus three adult and three small 

 prawns taken the day before (July 27th) were placed (on 

 July 28th) in a '^ water-circulator " dish containing Ulva 

 and other finer green weed, and exposed to diffuse light. 

 One of the adults, a dark ''fascigera " mottled with grey, 

 underwent no change during the experiment, which lasted 

 till August 1st, A second adult became of a lighter brown 

 colour, developed a temporary green tint, but became brown 

 again on July 31st, on which day it died. The remaining 

 adult became dark green on the 29th. Of the three small 

 prawns two had become bright green by the 29th, 



The opposite change from green to brown is well shown in 

 the case of Prawn d in Flask B (Table II, p. 662) , On July 

 22nd this green specimen was placed with brown weed, and 

 on the 25th, after being exposed to alternate diffuse light and 

 darkness, was the same tint as the finer brown weed, 



A fourth example of our experiments on the influence of the 

 colour of the weed on colour-change of Hippolyte may be 

 given, viz. the effect of red weed (Delesseria) on green 

 prawns (Table IV, p. 672) , The microscopic appearances of 

 two green specimens were noted (August 8th). The prawns 

 were then placed with the red weed in a ''water-circulator " 

 jar in the open. The experiment began at 12.30 in bright 

 sunlight, but after half an hour the weather became dull and 

 cloudy. At 4 p.m. one prawn had become of a clear brown 



