Biological Molecules 



as, for example, the pintail, the spotbill, and the 

 mallard ; others from two ancestors. Some of 

 these hybrids were crossed with other hybrids, 

 and others with the parent forms, hence Bonhote 

 secured a number of hybrids, each of which had 

 a distinctive appearance ; but all the variations 

 appearing among the hybrids were found to start 

 on one or more of the pcecilomeres. 



Certain of the hybrids showed a resemblance 

 to one or other of the parent species, others were 

 unlike either parent, and resembled either no 

 known species or species other than their parents. 



When a hybrid shows a resemblance to a species 

 other than that to which either parent belongs, it 

 is said to exhibit the phenomenon of atavism or 

 reversion, the individual is supposed to have 

 been " thrown back " to an ancestral form. 



The true explanation of the phenomenon would 

 seem to be that, as the result of the crossing, 

 biological molecules in the fertilised egg have 

 been formed which, on development, give rise to 

 combinations of colour like those seen in other 

 species. 



Thus the phenomena of " mimicry " and " re- 

 version " are, we believe, due to the fact that in 

 the fertilised egg of both the pattern and its copy 

 a similar arrangement of biological molecules 

 obtains. If we regard the sexual act as re- 

 sembling in many respects a chemical synthesis, 

 the phenomenon need not surprise us. 



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