TRANSACTIONS OF SECTION D, 767 
factory evidence on the point, and it is not known what organs are affected, 
whether it is the actual gametes, or the reproductive glands, or some of the other 
organs concerned.! 
The other result of changed conditions which is certainly known is to induce an 
increased amount of variability of the genetic kind, though not immediately, often 
indeed not until after the lapse of some generations. On this point Darwin says : 
‘Universal experience shows us that when new flowers are first introduced into 
our gardens they do not vary; but ultimately all, with the rarest exceptions, vary 
to a greater or less extent’ (‘ Variation,’ii. p. 249).?, With regard to the variability 
thus induced, it is to be noticed that it is not confined to any particular organ, 
nor does it show itself in any particular way. On the contrary, the whole organi- 
sation is affected, and the variations are quite indefinite. 
To sum up the argument asit at present stands: (1) a change in conditions cannot 
affect the next generation unless the reproductive organs are affected ; (2) from a con- 
sideration of the facts of the case, it is almost inconceivable that the effect produced 
upon any organ of a given organism by a change of conditions should so modify the 
reproductive organs of that organism as to lead to a corresponding modification in 
the offspring without the latter being exposed to the same conditions; (3) the only 
effects, which are certainly known, of changed conditions upon the reproductive 
organs are (a) the production of sterility ; (6) an increase in genetic variability. 
As far then as our certain knowledge goes, it would appear that a change of 
conditions may have one or both of the following effects :— 
(1) A definite change, of the same character or nearly so, in all the individuals 
acted upon. Such changes may be adaptive or non-adaptive, but they are not 
permanent, lasting only so long as the change of conditions, or at most during the 
ife of the individual acted upon. They are not transmitted in reproduction, and 
do not appear in the offspring unless it is submitted to the same conditions. These 
variations are the direct result of the action of the environment upon the indivi- 
dual, with the exception of the reproductive organs. 
(2) Increase in the variations of the genetic kind. These are seen not in the 
generation ° first submitted to the changed condition, but in the next or some 
subsequent generations. The effect is produced through the reproductive organs. 
These variations are non-adaptive, and different in each individual. 
If the reproductive organs are affected we get an increase in the variations of 
the genetic kind. These, we have seen, are usually of an indefinite character; they 
are different in every case, and their nature cannot be predicted from experi- 
-ence. But we still have to ask: Is this a universal rule? Does it never happen 
that a change of conditions so affects the reproductive organs as to produce a defi- 
nite non-adaptive change of the same character or nearly so in all the descendants 
of the individual acted upon? This is the most obscure question connected with 
the study of variations. If such changes occur, they might be cumulative, being 
increased in amount by the continued action of the conditions. They would be 
non-adaptive, their nature depending on the constitution of the reproductive cells 
and having no functional relation to the original stimulus. 
As possible examples of such variation, I may recall those variations referred 
to by Darwin as ‘fluctuating variations which sooner or later become constant 
1 The exact cause of this sterility in the higher animals is a point which specially 
needs investigation. 
? The phenomenon of increased variability following upon change of conditions 
has most often been observed when the change has been from a state of nature toa 
state of cultivation. Hence the conclusion has been drawn that the kind of change 
involved in domestication alone induces variation. But there is no evidence in 
favour of this view. The evidence shows that change of conditions in itself may 
induce greater variability. 
3 No doubt the individuals of the generation first submitted to the changed condi- 
tions would be affected as regards their reproductive organs, which would be altered 
in structure, but this has not been made out, though there are indications of such an 
effect in certain plants, vide Appendix. 
