ORIGIN OF COLOUR-VARIETIES 171 



compound or simple colours are produced, and, as we 

 have seen, the basal pigments — red and yellow — are 

 related to a colouring that, either external or internal, 

 is a thread binding all classes of animals and plants 

 together, and leading the mind to that ancient nutritive 

 significance which such pigments possess. In the 

 case of this prawn that nutritive value is especially 

 clear. As we can assign to the colouring matter 

 and the light-position of the seaweed their several 

 parts in the production of plant food, so to the similar 

 colour and equal immobility of the prawn we can 

 attribute a corresponding though lower economic im- 

 portance ; and the causes that have favoured the green 

 colour of sea-grass have been also active in producing 

 the green colour of the prawn that rests thereon. 



Yet with such sapient conclusions we are not 

 content. Animals are by nature active creatures, and 

 the spectacle of a prawn thus vegetating and growing 

 into its surroundings pricks the mind to ask how the 

 process works. Does a green prawn give rise to green 

 young, and a red prawn to red young, or is there no 

 hereditary bias in favour of any one colour, and the 

 matter left to the choice of the children ? And how 

 comes that banding and dappling which fits the prawn 

 to its weed ? The answers to such questions are slow 

 in coming to a satisfactory fulness, though already 

 much is known. Hippolytc issues upon life not in the 

 image of its mother, but as a minute colourless creature, 

 with none of the walking legs it will afterwards possess, 

 and provided with swimming limbs and a flexible tail 



