340 
its presence and its absence. Hence his well-known Presence and Absence 
theory. In this case (T) is allelomorphie to its absence (t). The inheritance 
of combs in chickens is a beautiful application of such a conception. Muta- 
tions according to this theory appear as the result of losses. 
Bateson pushed this idea to its logical conelusion in his Melbourne ad- 
dress where he speculates on the possibility that evolution has come about 
by the loss of something. These somethings he assumes to be inhibitors. 
(Science, August 28, 1914). 
“ As I have said already, this is no time for devising theories of 
evolution, and I propound none. But as we have got to recognize that there 
has been an evolution, that somehow or other the forms of life have arisen 
from fewer forms, we may as well see whether we are limited to the old view 
that evolutionary progress is from the simple to the complex, and whether 
after all it is conceivable that the process was the other way about. 
> At first it may seem rank absurdity to suppose that the prim- 
ordial form or forms of protoplasm could have contained complexity enough 
to produce the divers types of life. 
iN Let us consider how far we can get by the process of removal 
of what we call “‘epistatic’’ factors, in other words those that control, mask, 
or suppress underlying powers and faculties. 
ms I have confidence that the artistic gifts of mankind will prove 
to be due not to something added to the make-up of an ordinary man, but to 
the absence of factors which in the normal person inhibit the development 
of these gifts. They are almost beyond doubt to be looked upon as releases 
oe 
of powers normally suppressed. The instrument is there, but it is ‘stopped 
down.” The scents of flowers or fruits, the finely repeated divisions that give 
its quality to the wool of the merino, or in an analogous case the multiplicity 
of quills to the tail of the fantail pigeon, are in all probability other examples 
of such releases. 
~ In spite of seeming perversity, therefore, we have to admit 
that there is no evolutionary change which in the present state of our knowl- 
edge we can positively declare to be not due to loss. When this has been con- 
ceded it is natural to ask whether the removal of inhibiting factors may not 
be invoked in alleviation of the necessity which has driven students of the 
domestic breeds to refer their diversities to multiple origins.” 
Another idea as to the way these factors may find expression in the germ 
cells has been advanced by Morgan under the heading of Multiple Allelo- 
