Not only, however, is Weismann's principle of "Amixia" thus very differently stated from that of my "Independent Variability" (apogamy), or Gulick's "Independent Generation"; but, apparently owing to this difference of statement, the principle itself is not the same. In particular, while Weismann holds with us that when new characters arise in virtue of the mere prevention of intercrossing with parent forms these new characters will be of non-utilitarian kind[47], he appears to think that divergence of character under such circumstances is not likely to go on to a _specific_ value. Now, it is of importance to observe why he arrives at this conclusion, which is not only so different from that of Delbœuf, Gulick, and myself, but apparently so inconsistent with his own recognition of the diversifying effect of "Amixia" as regards the formation of _permanent varieties_. For, as we have already seen while considering Darwin's views on this same principle of "Amixia," it is highly inconsistent to recognize its diversifying effect up to the stage of constituting fixed varieties, and then not to recognize that, so much divergence of character having been already secured by the isolation alone, much more must further divergence continue, and continue at an ever accelerating pace--as Delbœuf and Gulick have so well shown. What, then, is the explanation of this apparent inconsistency on Weismann's part? The explanation evidently is that, owing to his erroneous statement of the principle, he misses the real essence of it. For, in the first place, he does not perceive that this essence consists in an initial difference of average characters on the part of the isolated colony as compared with the rest of their species. On the contrary, he loses himself in a maze of speculation about all species having had what he calls "variation-periods," or eruptions of general variability alternating with periods of repose--both being as unaccountable in respect of their causation as they are hypothetical in respect of their occurrence. From these speculations he concludes, that isolation of a portion of a species will then only lead to divergence of character when the isolation happens to coincide with a "variation-period" on the part of the species as a whole, and that the divergence will cease so soon as the "variation-period" ceases. Again, in the second place as previously remarked, equally with Wagner whom he is criticizing, he fails to perceive that _geographical_ isolation is not the only kind of isolation, or the only possible means to the prevention of free intercrossing. And the result of this oversight is, that he thinks amixia can act but comparatively seldom upon sufficiently small populations to become a factor of much importance in the differentiation of species. Lastly, in the third place, owing to his favourite hypothesis that all species pass through a "variation-period," he eventually concludes that the total amount of divergence of type