The two polar cells are therefore, on this view, of totally different character; and the nuclear division in each case of a special kind and _sui generis_. I do not think that the evidence afforded by observation lends much support to this view. But with that we are not here specially concerned. We have to consider how this reduction of the number of ancestral germ-plasms can further the kind of variation required. Now, it is difficult to see, and Professor Weismann does not explain, how the getting rid of certain ancestral tendencies can give rise to new characters or the enhancement of old characters. One can understand how this "reducing division," as Dr. Weismann calls it, can reduce the level of now one and now another character. But how it can raise the level beyond that attained by either parent is not obvious. It is perhaps possible, though Professor Weismann does not, I think, suggest it, that, by a kind of compensation,[BT] the reduction of certain characters may lead to the enhancement of others. Let us revert to the illustration on p. 150, where each individual has an available store of forty units of growth-force; and let us express by the minus sign the units lost in the parents by the extrusion of the polar cell and an analogous process which may occur in the genesis of the sperm. Then the units of growth-force which may thus be lost by a "reducing division" in _b_, _c_, and _e_ may be, in the offspring, applied to the further growth of _a_; thus-- Parents. Offspring. -------/\------ | | _a_ 10 10 14 _b_ 8-1 10-3 7 _c_ 9-1 5-1 6 _d_ 7 9 8 _e_ 6-2 6 5 Here the reduction of the characters _b_, _c_, and _e_ has led to the enhancement of _a_, which thus stands at a higher level than in either parent. On such an hypothesis we may, perhaps, explain the fact to which breeders of stock testify--that the organ strongly developed in both parents (_a_) is yet more strongly developed in some of their offspring, and that weakly parts (_e_) tend to become still weaker. I know not whether this way of putting the matter would commend itself to Professor Weismann or his followers; but some such additional hypothesis of transference of growth-force from one set of organs to another set of organs seems necessary to complete his hypothesis.