On the other hand, the sudden first appearance of a saltatory variation takes place quite independently of personal selection, depending on similar variations in a number of ids, which remain latent until they have by the process of reducing division which precedes amphimixis, chanced to attain a majority. In sudden bud-variations we may perhaps suppose that reducing division occurring in some still unverified abnormal manner is the reason why the germinal variation suddenly makes itself visible--a supposition previously suggested as the explanation of the reversion of these sports. The rarity of bud-variation is thus explained, while the greater frequency of saltatory variations in plants propagated by seed may be accounted for by the regular occurrence of reducing division in sexual reproduction. But that the same or similar variations may occur in several, it may be in many, ids at the same time must depend upon similar general influences which affect the plant as a whole, as happens through cultivation, manuring, and so on. I shall return to this when discussing the influence of the environment. In some quarters this whole conception of germinal selection has been characterized as the merest figment of imagination, condemned on this ground alone, that it is based on the differences in nutrition between such extremely minute quantities of substance as the chromosomes of nuclear substance within the germ-cell. The quantity of substance is certainly minute, but it needs nutriment none the less, and can we believe that the stream of nourishment for all the invisibly minute vital elements is exactly alike? It may be admitted that the nourishment outside the ids is usually abundant, although undoubtedly fluctuations occur in it also, but it certainly does not follow from this that every vital unit within the id is similarly disposed in relation to the nutritive supply, or has food in equal quantities at its command, or even that each has as much as it can ever need. To make an assertion like this seems to me much the same as if an inhabitant of the moon, looking at this earth through an excellent telescope and clearly descrying the city of Berlin with its thronging crowds and its railways bringing in the necessaries of life from every side, should conclude from this abundant provision that the greatest superfluity prevailed within the town, and that every one of its inhabitants had as much to live upon as he could possibly require.