560 
E. EUGGLES GATES AND NESTA THOMAS. 
Fluctuations we may define by contrast as continuous 
changes arising from tlie effects of environment or nutrition 
which are only partly inherited and hence which show Gal- 
tonian regression^ the whole population forming a continuous 
series in regard to a fluctuating character. 
Mutations and fluctuations are thus contrasted in several 
particulars. As regards inheritancej they are botli inherited^ 
but in different degrees and in different ways. In this view 
I am in agreement with Professor E. B. Poulton (see “ The Term 
^ Mutation/^’ ^ Proc. Section 1 ), British Association/ 1913), 
and regard it as a mistaken conception to hold, as has fre- 
quently been done, particularly by the Mendelian school, that 
mutations are inherited while fluctuations are not. In the 
discussion following Professor Poultonhs paper, I suggested 
that the terms partial and complete inheritance should be 
used with reference to fluctuation and mutation respectively. 
That is, mutations ai’e completely inherited either in all the 
offspring, or at least in a portion of them with reversion in 
the others ; while fluctuations ai-e partially inherited in 
varying degrees in the offspring, and thus form a continuous 
graded series ranged on one or both sides of the parental 
condition according to the place occupied by the parent orga- 
nism in the original series. 
It is probable that in addition to these partially inherited 
fluctuations there are also non-inherited or somaticfluctuations. 
Mutations are also contrasted with Mendelian metathesis 
or recombinations. The former deal with the origin of new 
and discontinuous characters, while the lattei* are concerned 
merely with the combinations and permutations of such 
characters as have already appeared. Obviously, then, 
Mendelism sensu s trie to is not concerned with the origin 
of new unit-characters. The sudden origin of a character 
constitutes a mutation ; its inheritance may be Mendelian 
or otherwise, but is in any case a process distinct from the 
change which brought about its origin. In this aspect muta- 
tion deals with discontinuous origins and Mendelism with 
discontinuous inheritance. 
