xii Proceedings. \January 12th, igog. 



and upon which it feeds. Previous experiments made jointly 

 by the author and Professor Keeble have shown that this 

 remarkable sympathetic colouration is in all probability not 

 inherited — i.e., the colour-varieties do not necessarily breed true, 

 but that the harmonious motley exhibited by this varying species 

 is the outcome of a very special colour adaptation acquired by 

 each individual, and that the colouration is controlled largely 

 by the colour of the weed at the time when the young prawn 

 settles down upon it, after a brief free-living larval existence. 



The results of more recent researches by the author on this 

 subject have shown that the amount of red pigment in the larva 

 varies, in all races but the green one, with that in the parent. 

 The more there is of it in the parent, the more highly coloured 

 is the offspring. Green parents, however, gave rise to three 

 kinds of broods: (i) highly coloured ones like those of brown 

 parents, (2) pale ones, and (3) a mixed brood, containing 

 coloured to colourless in the proportion of 3 : i. This result 

 tends to show that green Hippolyte are derived (i) from brown 

 individuals that have been transformed into green, after migrat- 

 ing from brown to green weed; (2) from green individuals that 

 have remained on their weed, and (3) from a cross between 

 these kinds. 



Further experimental results were obtained on the pro- 

 longed influence of light on the colouration of this animal 

 both when white light was reflected on the young Hippolyte 

 from a porcelain dish, and also when the young animals 

 were kept in coloured light (red or green). In the former case 

 the existing pigments (red and yellow) gradually disappeared 

 from the greater portion of the animal, and at length, after a 

 month's interval, only one strip of pigment remained, but this 

 formed a dense .screen around the nervous system. This screen 

 is probably of considerable physiological significance, as it is 

 found in many of the lower Crustacea, and also in many worms. 



The coloured light experiments yielded an unexpected result, 

 namely, a complementary colour to that of the light employed. 

 Thus, under the influence of green light for a month, Hippolyte 



