Nov., 1889. 
THEORIES OF HEREDITY. 
249 
expect that mutilations, especially such as were inflicted early 
in life, would be transmitted to offspring ; for all the cell- 
generations later than the date of the injury would be 
absent, and therefore unrepresented by gemmules. But 
there is no evidence in favour of the transmission of mutila¬ 
tions, however early they may be inflicted. All the evidence 
when carefully examined points in the opposite direction. 
Furthermore, in the process of transfusion, when the 
blood of one individual is replaced by that of another, it 
seems reasonable to suppose that, if the gemmules exist, 
many of them would be carried over, and would collect in 
the germ-cells of the individual which received the blood, 
and that thus some characters of one individual would after¬ 
wards appear in the offspring of another. Careful experi¬ 
ments, conducted by Galton and later by Komanes, prove 
that such transference of hereditary characters does not 
accompany the transfusion of blood. 
Not onlv mav blood be transfused, but various tissues 
may be grafted and will thrive on another individual, or even 
on a very different species. In these cases, too, we should 
expect that such transferred tissues would produce effects 
upon the offspring, for, according to the hypothesis, they 
would continue to give off gemmules. No such hereditary 
influence has ever been traced or even rendered probable. 
When we enquire why Darwin was led to frame such a 
hypothesis, which, in spite of its great merit in connecting- 
together a number of apparently isolated facts, has so much 
to be said against it, we find the answer in a reply to one of 
Huxley’s letters, in which Pangenesis had evidently been 
adversely criticised. Darwin says (“Life and Letters,” first 
edition, 1887, Yol. III., p. 44): “ I do not doubt your judg¬ 
ment is perfectly just, and I will try to persuade myself not 
to publish. The whole affair is much too speculative; yet I 
think some such view will have to be adopted, when I call to 
mind such facts as the inherited effects of use and disuse, &c.” 
This opinion of Darwin’s is as true to-day as when it was 
written (about 18G5, exact date uncertain). If the effects of use 
and disuse are transmitted, the explanation must be sought for 
in a hypothesis constructed on the same lines as Pangenesis. 
But if we are mistaken in believing that such transmission 
occurs, a far simpler hypothesis will account for the facts. 
The manner in which the transmission of such effects can 
be explained by the hypothesis of Pangenesis is shown in 
Diagram I. Two of the somatic cells, I on the right side 
and N on the left, are dark coloured. This is to represent 
some change which lias been wrought in their structure by 
