Biological Molecules 



white dress, is (although the change is from 

 brown to white) again conducted along precisely 

 similar lines." Mr Bonhote argues with great 

 force that, as the process occurs in two animals 

 so widely separated, the fundamental cause must 

 be a deep-seated one. There can be no doubt 

 that these pcecilomeres of Bonhote are connected 

 with our biological molecules. Each of these 

 pcecilomeres is the result of the development 

 of one of these unit characters ; each is to be 

 regarded as the centre of activity, the sphere of 

 influence of a biological molecule, or the portion 

 of one, which controls the colouring of a definite 

 region of the organism. In the case of creatures 

 which display the same colour throughout, these 

 molecules all give rise to the same kind of 

 colouring ; in the case of animals which display 

 a variety of colours and markings the various 

 molecules give origin to various colours. But 

 we must bear in mind that the final colour to 

 which each colour-producing molecule gives rise 

 depends to some extent on circumstances other 

 than the constitution of the molecule. Thus it 

 is that the young in most organisms differ in 

 colour and marking from the adults. On this 

 also depends the phenomena of seasonal and 

 sexual dimorphism. The same colour-producing 

 molecule may give rise to one colour under one 

 set of conditions and to a totally different colour 

 under another set of conditions. 



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