Mr. Darwin’s hypothesis of Pangenesis implies not only that the reproductive cell must contain numerous kinds of gemmules derived from different organs, but that the numbers of these gemmules must bear to one another something like the proportions which the originating organs bear to one another in size. The conception involves many different kinds, whose numbers are in many different proportions, and I supposed the difficulty alleged was, that for the influence of a previous sire to be communicated from the growing fœtus to the mother would imply not only the transfer of the various kinds of gemmules derived from him, but also maintenance of their numerical proportions, and that again these gemmules, diffused throughout the maternal system, would have to be transferred in these proportions to the subsequently formed ova. No such difficulties arise if the units conveying hereditary characters are of one kind only.
From this it is apparent that Mr. Spencer has misunderstood “the difficulty alleged,” and that the desired explanation is not yet forthcoming. I did not say anything about “kinds” or “proportions” of the carriers of heredity; my difficulty is to conceive of any mechanism whereby these carriers can first directly influence the somatic-cells of the mother, and then indirectly reflect this influence upon her germ-cells. Also, I cannot see any obvious necessity for the intervention of the “embryo” in the process.
GLOSSARY.
Acquired characters.—See Somatogenetic characters.
Amphigony (Häckel).—Sexual reproduction.
Amphimixis (Weismann).—The mingling of the hereditary substances of two individuals in an act of sexual union.
Ancestral germ-plasm.—See p. 123.