HIPPOLYTE VARIANS. 617 



chromatoplioric habit at the point where^ being overtaken by- 

 night, it had been compelled to leave it at the close of the 

 previous day. That this is so we prove in the section on 

 Nocturnal Colour. We suggest that a change owing to 

 change of weed, for example, which may not have had time 

 to express itself before nightfall on the previous day, may 

 make its appearance as a modification of colour on the day 

 ensuing. The argument may seem extravagant, though less 

 so, we think, than the fact, and less, too, when the section 

 on Nocturnal Colour has been perused. 



Effect of Change in Light Intensity. — Though the 

 prawns offer no quick change of colour in response to colour- 

 change in their weed, preferring ordinarily to change their 

 habitat rather than their habit, they offer a series of re- 

 markable colour responses to well-marked changes in light 

 intensity or light distribution. Professor Herdman has sug- 

 gested that the lack of sympathetic colour-change in response 

 to change of colour of the accompanying weed is attributable, 

 at all events in part, to the dulness of light conditions at 

 Piel. The facts with which we now deal seem, however, to 

 point away from that suggestion. 



The following observations indicate the pronounced nature 

 of the colour-change which alteration of illumination induces 

 in Hippolyte varians. The specimens, taken (August 

 15th, between 4 and 6 p.m.) from the trawl or bottom 

 tow-net, were at once divided into four lots, each lot con- 

 taining representatives of the various forms obtained. These 

 four lots were disposed as follows (Table V, pp. 674 — 676) : — 

 (A) in clear glass jar left standing open on deck, (B) in a 

 glass ]'ar covered with fine muslin, (C) in a white porcelain 

 jar with muslin cover, (D) in a blackened jar with black 

 cover. The jars A, B, C, D all contained fresh sea water 

 but no weed. After an hour the specimens in B (glass jar 

 with muslin cover), and especially in C (porcelain jar muslin 

 covered), were found to have undergone a marked change, 

 whilst those in A (clear glass jar) and in D (dark) were prac- 

 tically unaltered. We have repeatedly tried the experiment 



