Darwin, and After Darwin, Volume 2 of 3: Post-Darwinian Questions: Heredity and UtilityRomanes, George John
Science
Darwin, and After Darwin, Volume 2 of 3: Post-Darwinian Questions: Heredity and Utility
Romanes, George John
Evolution (Biology); Heredity
Here, it will be observed, there was no selection; and therefore the
increased hereditary effect in the second generation must apparently be
ascribed to a continuance of influence exercised by somatic tissues on
germinal elements; for at the time when the changes were produced no
seed had been formed. In other words, the accumulated change, like the
initial change, would seem to have been exclusively of somatogenetic
origin; and yet it so influenced the qualities of the seed (as this was
afterwards formed), that the augmented changes were transmitted to the
next generation, part for part, as the lesser changes had occurred in
the preceding generation. "This experiment, therefore, like Professor
Buckman's, shows that the alteration of the tissues was carried on in
the second generation from the point gained in the first. In both cases
no germ-plasm (in the germ-cells) existed at the time during which the
alterations arose, as they were confined to the vegetative system; and
in the case of the parsnips and carrots, being biennials no germ-cells
are produced till the second year has arrived[77]."
[77] I am indebted to the Rev. G. Henslow for the references to
these cases. This and the passages which follow are quoted from
his letters to me.
Once more, Professor Bailey remarks:--
"Squashes often show remarkable differences when grown upon
different soils; and these differences can sometimes be perpetuated
for a time by seeds. The writer has produced, from the same parent,
squashes so dissimilar, through the simple agency of a change of
soil in one season, that they might readily be taken for distinct
varieties. Peas are known to vary in the same manner. The seeds of
a row of peas of the same kind, last year gave the writer marked
variations due to differences of soil.... Pea-growers characterize
soils as 'good' and 'viney.' Upon the latter sort the plants run to
vine at the expense of the fruit, and their offspring for two or
three generations have the same tendency[78]."
[78] _Gardener's Chronicle_, May 31, 1890, p. 677.
I think these several cases are enough to show that, while the
Weismannian assumption as to the seeming transmission of somatogenetic
characters being restricted to the lowest kinds of plants is purely
gratuitous, there is no small amount of evidence to the contrary--or
evidence which seems to prove that a similar transmission occurs
likewise in the higher plants. And no doubt many additional cases might
be advanced by any one who is well read in the literature of economic
botany.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account