Note 67 — Chapter V
Reading edition
In fact, it seems to me that this is the sole supposition whereby it can be held that sexual propagation has been developed both “by” and “for” natural selection, in order to supply variations as material for the action of this principle. Natural selection cannot thus supply the conditions to its own activity, if, as Weismann supposes, there is but one purpose for it to subserve (see above, pp. 13-15). But, if it is acting for more than one purpose, the “by” and the “for” argument may hold.