these which present sufficiently well-marked varieties for the purpose. But, pending the successful accomplishment of this particular experiment in the grafting of any animal tissue, I think it would be clearly unjustifiable to conclude against the Lamarckian factors on the ground of any other experiments yielding negative results in but one generation or even in a large number of sequent generations. For instance, the latter consideration applies to the negative results of Mr. Francis Galton's celebrated _Experiments in Pangenesis_.[82]. These consisted in transfusing the blood of one variety of rabbit into the veins of both sexes of another, and then allowing the latter to breed together: in no case was there any appearance in the progeny of characters distinctive of the variety from which the transfused blood was derived. But, as Mr. Galton himself subsequently allowed, this negative result constitutes no disproof of pangenesis, seeing that only a portion of the parents' blood was replaced; that this portion, even if charged with "gemmules," would contain but a very small number of these hypothetical bodies, compared with those contained in all the tissues of the parents; and that even this small proportional number would presumably be soon overwhelmed by those contained in blood newly-made by the parents. Nevertheless the experiment was unquestionably worth trying, on the chance of its yielding a positive result; for, in this event, the question at issue would have been closed. Accordingly I repeated these experiments (with the kind help of Professor Schäfer), but with slight differences in the method, designed to give pangenesis a better chance, so to speak. [82] _Proc. R. S. 1871._ Thus I chose wild rabbits to supply the blood, and Himalayan to receive it--the former being the ancestral type (and therefore giving reversion an opportunity of coming into play), while the latter, although a product of domestication, is a remarkably constant variety, and one which differs very much in size and colour from the parent species. Again, instead of a single transfusion, there were several transfusions performed at different times. Moreover, we did not merely allow the blood of one rabbit to flow into the veins of the other (whereby little more than half the blood could be substituted); but sacrificed three wild rabbits for refilling the vascular system of each tame one on each occasion. Even as thus improved, however, the experiment yielded only negative results, which, therefore, we never published.