110 Proceedings of Royal Society of Edinburgh. [sess. 
cases in the present discussion, since Weismann expressly 
allows that in long-continued conditions affecting the whole 
system the germinal cells may he directly affected along 
with, though not exactly by, the other elements of the 
organism. 
(3) A criticism of a different nature has been suggested by several, 
hut is well stated by Eimer. If the source of variation 
be restricted by hypothesis to the keimplasma intermingled 
in sexual reproduction, is this sufficient to account for the 
facts 1 “In what way, one must ask, have new characters 
first been introduced into the series 1 The sexual mixture 
could produce nothing ; it could only work with what was 
already given.” Professor M ‘Kendrick has forcibly empha- 
sised a similar objection. There is no doubt, at any rate, 
that Weismann’s theory, which excludes the direct assistance 
of environmental and functional variations, throws a still 
heavier burden than Darwin did on the shoulders of Natural 
Selection, which many believe to be already somewhat over- 
weighted. 
Without urging concrete cases, in regard to which one cannot but 
allow the necessity of fresh observation; without venturing on the 
pathological field where authorities like Virchow and Ziegler so 
much differ ; without urging difficulties from the general theory of 
evolution, I wish to emphasise what appears to me to be the physio- 
logical compromise at present tenable. Does the doctrine of the 
continuity of the reproductive protoplasm really force one to deny 
the transmission of acquired characters 1 Stable and persistent as 
the keimplasma may be, can one believe that it leads a charmed 
life in the general symbiosis of the organism 1 Are the reproductive 
cells in so rigid a degree insulated from the general life 1 
(1) Every one allows the general conception of the various organs 
as symbions in a common life. We constantly speak of cor- 
related variations, and though these generally work from the 
centre or germinal plasma outwards, there is no a priori 
improbability against an environmental influence of some 
strength saturating through the entire organism, affecting 
one system by another, till eventually the reproductive cells 
share in the change. 
