HIPPOLYTE VARIANS. 621 



It might be thought that this surprising result is due to 

 the " light filters " transmitting a very feeble light, practi- 

 cally only equivalent to dimness. We have endeavoured by 

 the use of incandescent light and reflectors to bring the 

 coloured light up to a high degree of intensity, and the results 

 are the same as when daylight is employed. 



We conclude, then, that whereas light-intensity plays a 

 considerable part in determining the colour patterns, the 

 quality of light has no effect ; a conclusion which harmonises 

 with that derived from our observations on the small effect 

 of different coloured weeds in modifying the colour. It seems, 

 then, that this small and very slowly effected change is in all 

 probability due to response to the different intensities of the 

 light reflected from the differently coloured surfaces of the 

 red, green, or brown weeds. 



A possibility, however, remains — that the quality of light 

 may exert a directive effect on Hippoly te ; may, failing to 

 cause it to change its spots, cause it to change its position. 

 Though we have endeavoured to obtain evidence as to the 

 truth of this conjecture we have not yet succeeded. So far 

 as our experiments have yet proceeded we find that, though 

 the possession of a " colour sense " has been ascribed to so 

 lowly a Crustacean as Daphnia, we have no need, even 

 though we had the desire, to make a similar demand on 

 behalf of Hippoly te varians. We may, therefore, refrain 

 from discussing what exactly the term '^ colour sense" would 

 imply with respect to a Crustacean. 



Conclusion. — Hippolyte varians is a parasite on sea- 

 weeds and zoophytes. On these it finds both food and shelter. 

 Its prime object in life is to anchor itself. Once fixed, rather 

 than release its hold it will allow the ebb-tide to leave it 

 stranded. By its immobility it has grown into its surround- 

 ings and become coloured like them. Should it be forcibly 

 separated from its favourite weed its movements become of an 

 aimless sort. Its nervous system is thrown out of gear, so that 

 it does not, at least for a time, exhibit the phytotaxic irritability 

 which we believe it (for reasons given on p. 594) to possess. 



VOL. 43, PART 4. — NEW SERIES. X X 



