Recent Advances in the Study of Heredity. 323 
remotely related forms are crossed the equilibrium of both is 
disturbed to so great an extent that the hybrid has, so to speak, to 
go a long way back before it can get a firm foothold again, 1 and 
then we get a case of what we call reversion. But if the two 
forms are not so remotely related the disturbance is not so great and 
the result is that the hybrid does not fall further back than on one of 
the two parents, and we get what we call dominance. The difference 
between the two cases may be expressed in another way, which will 
be more repulsive than the last to those who think that sober 
ratiocination is the only method of elucidating the truth. In the 
case of a cross between remotely connected forms, the disturbance 
caused by their union is so great that neither of them can keep 
their heads, with the result that the hybrid reverts to the first 
solid thing in the memory, that is to say the racial memory, of the 
zygote ; whereas in the case of the union of two closely related 
forms the disturbance is not so great that one of them at least 
cannot keep its head and impress its characteristics upon its off¬ 
spring. I am quite aware of course that an idea of this kind will 
be rejected as unscientific; but the idea rose up in my mind as I 
was paying attention to the point in question and I am not by any 
means convinced that an apparently extravagant analogy of this 
kind is any more remote from the real state of affairs than the 
hypotheses which find favour with modern professional men of 
science. It is, however, perhaps advisable to return to the 
conventional sphere of thought. An objection which is likely to be 
raised straight away to the suggestion that there is no such thing 
as a 3 : 1 or a 1 : 2 : 1 proportion, and that all of them are really 
instances of 3 : 9 : 4 is, that in all cases of 3:9:4 the hybrid is 
a reversionary one, i.e., it bears the character of some remote 
ancestor, so that the result of F x is amply sufficient to prove not only 
that it belongs to one or the other category, and hence that the two 
are radically distinct, but also to which of the two it belongs. The 
answer to this is, in the first place, that the ratio 1 : 2 : 1 is not 
always associated with simple dominance in F 1? as in the case of 
the Andalusian fowl. Inasmuch therefore as the character of the 
Andalusian may be dependent for its manifestation on the co¬ 
existence in the zygote of two factors, one of which existed in the 
splashed white and the other in the black, there is nothing but an 
estimation of the ratio by the statistical formula referred to to show 
1 The answer to the complaint, which the reader may make, that 
this is too metaphorical is that the signification of the terms 
heredity and reversion are as metaphorical as can be. 
