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 a// the variations 
appearing among the hybrids were found to start 
on one or more of the peecilomeres. 
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 toa 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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