1 82 PHYSIC 



cess allied to but, so far as yet known, without the agency 

 of a nervous system, unless it be a rudimentary sympa- 

 thetic, in determining and producing the magnificent array 

 of colouration displayed throughout the vegetable king- 

 dom. 



The superficies of each animal is vitalised by the peri- 

 pheral nerves, the texture of that superficies being deter- 

 mined and its colour resolved upon and fixed in settled 

 perpetuity, so far as the individual animal is concerned, 

 by the inherent determining and selective powers of the 

 nervous system, reacted upon by the conditions of its 

 environment, and the chemical and physical nature of the 

 pabulum with which it is supplied, by the pervading and 

 related haemal vascular system and nutritional mechanism ; 

 in other words, by the laws of natural selection, which here 

 operate with great conspicuousness and continuity of pur- 

 posive design the colour of the deep-seated, as well as 

 the superficial parts, must necessarily be determined and 

 perpetuated by like agencies. 



In the embryo are laid the foundations of the colour, 

 shape, and general characteristics of the future organism, 

 and the molecular arrangements, cellular development, and 

 the manner of unfolding of its component parts, organs, 

 and appendages foreshadowed and determined. In early 

 and mature age are wrought out the designs formed in 

 the embryo, while in old age we witness their modification, 

 involution, and obliteration to meet the altered and alter- 

 ing circumstances of the individual organism and its 

 environment. 



Colour, being not a property of matter, but the outcome 

 of its molecular arrangement, the causes of its changes 

 and disappearance in the living body, must, therefore, be 

 sought for amid the incessant activities and processes of 

 vital synthesis and analysis of integration and disintegra- 

 tion, growth and decay, which repeat themselves in regular 

 succession during the course of life. Continuity and 

 regularity, in these conditions and processes, must be 

 followed by sameness of result, and, consequently, same- 

 ness of colour, while discontinuity and irregularity must 

 be followed by difference of result, and, consequently, 

 difference of colour, which latter occurrence must be quite 



