DEVELOPMENT OF COLOUR-PATTERN 173 



prawn agree, however different may be the colour of 

 their parents. At birth, therefore, Hippolyte has no 

 hereditary bias towards this colour or that. 



After a life of some days spent offshore among 

 the flotsam of the sea, the young Hippolyte, still 

 transparent and almost colourless, is carried inshore, 

 and attaches itself to the first thing that comes handy. 

 If in deep water, the holdfast will be a red weed ; if 

 within the tidal zone, it will chance upon one of the 

 many variegated bushes that clothe the rocks ; if 

 among the tangles and dense Fucus, a brown weed will 

 be the likeliest anchorage. 



On whatever hold it chances the young animal 

 will stay, partly to feed, partly to avoid dislodgment and 

 death by the surf. At this stage its skin is of a great 

 sensitiveness. Experiment shows that if two com- 

 panies of such colourless young Hippolyte are supplied 

 respectively with contrasting weeds, each will assume 

 the corresponding tint in a day, and the colour so 

 formed will increase in intensity until the match is 

 complete. 



So on the beach, as the light filters down to where 

 the young Hippolyte cling like stranded mariners 

 to the slippery rocks, the prawns respond to the 

 colour of their environment, and before a week is 

 over the resemblance is complete ; and should a gale 

 or a low spring-tide set them moving, they will not 

 be long before selecting cover that corresponds with 

 their coat. All have the colour-scale before them, 

 and their choice is made at the start of their career. 



