766 REPORT—1899. 
will be so slight as not to be noticeable. Now, we know that homologous parts, 
whether symmetrically homologous or serially so, are in some kind of close con- 
nection. For instance, when one member of an homologous series varies, it is 
commonly found that other members of the same series will also vary. Yet in 
spite of this connection which exists between the right and left arms and between 
the right arm and right leg, there is no similar alteration either in the left arm or 
in the right leg. Now, if parts which from these facts we may suppose to be in 
some connection are not affected, how can we expect the reproductive organs not 
only to be modified, but also to be so modified that the germs which are about to 
be budded off from them will be so affected as to produce exactly the same 
character—in this case enlarged muscle, &c.—without the application of the same 
stimulus, viz. exercise? Thus, while I freely admit that every alteration of an 
organ in response to external agents will react through the whole organisation, 
affecting each organ in functional correlation with the affected organ in a way 
which will depend upon the function of the correlated organ, and possibly other 
organs not in functional correlation in an indefinite way and toa slight extent, 
yet I maintain that it is very hard to believe that it will have such a sharp and 
precise effect upon every spermatozoon and ovum subsequently produced that not 
merely will these products be altered generally in all their properties, but that one 
particular part of them—and that part of them always the same—will be so 
altered that the organisms which develop from them will be able to present the 
same modification on the application of a different stimulus. It is inconceivable ; 
unless, indeed, we suppose that the very molecules of the incipient organs in the 
germ are more closely correlated with corresponding parts of the parent body 
than are the homologous parts of the parent body with one another. 
Now, to prove the existence of such a remarkable and intimate correlation 
would surely require the very strongest and most conclusive evidence. Is there 
any such strong evidence? I think I may fairly answer this question in the 
negative. The evidence which has been brought forward in favour of the so- 
called inheritance of acquired characters is far from conclusive. That such 
evidence! exists I do not deny, but it is all, or almost all, capable of receiving 
other interpretations. 
Effect of Changed Conditions upon the Reproductive Organs. 
On the other hand, all the certain evidence we have concerning what happens 
when the reproductive organs are affected, either directly or by correlation, by a 
change of conditions—and, as we have seen above, they must be affected if there 
is to be any change in the offspring—tends to show that there is not any relation 
between the effect produced on the parent and that appearing in the offspring. 
The only means of judging whether the reproductive organs are affected by 
external conditions is by observing any change which may occur in their function. 
Now, only two such physiological effects of a change of conditions are certainly 
known; these are (1) the production of sterility or of partial sterility; (2) the 
production of an increased but indefinite variability in the offspring. With 
regard to the first of these effects: One of the most common, or at any rate one 
- of the most noticeable alterations in an organism, effected by change in the 
external conditions, is an alteration of the reproductive system, an alteration of 
such a kind that organisms which had previously freely interbred with one 
another are no longer able to do so. One of the most common results of removing 
organisms from their natural surroundings is to induce sterility or partial sterility. 
There is no reason to doubt that this sterility or tendency to sterility is, broadly 
speaking, due to an affection of the reproductive system. In the case of the 
higher animals, it may in some cases be due to an action upon the instincts, but 
in the lower animals and in plants we can hardly doubt that it is due to a direct 
action upon the reproductive organs. Indeed in plants these organs are often 
visibly atlected. Among animals, however, there does not appear to be any satis- 
1 For a ood statement and discussion of the evidence in favour of this view, see 
Romanes’s Darnin and after Darwin, vol. ii. chaps. 3 and 4. 
