LECTURE XXVIII 

 THE GENERAL SIGNIFICANCE OF AMPHIMIXIS 



Twofold import of amphimixis — It conditions tlie continual changing of indi- 

 viduality — Analogy from game of cards — The germ-plasm is at once variable and 

 persistent — The two roots of individual variation: germinal selection and new 

 combinations of the ids— 'Harmonious' adaptation conditions amphimixis — Difference 

 between adaptation and mere variation— Is a 'direct' use of amphimixis to be insisted 

 iipon? — Ceaseless intervention of personal selection in the lineage of the germ -plasm — 

 Far-reaching effects of personal selection — Fixing of the arrangements for amphimixis 

 in the course of generations of species — Increase of the constancy of a character -with its 

 dui-ation — Characters in the same ^i^ecies variable in different degrees — The ujiper and 

 under sm-faces of Kallima — Wild plants brought under cultivation do not at first vary 

 — Amphimixis very ancient, therefore very firmly established — Does amphimixis bring 

 about equalization (Hatschek, Haycraft, Quetelet) ? — Galton's frequency curves — 

 Ammon's free scope for variations — De Vries' assymetrical curves of frequency. 



We have already made ourselves familiar with the process which 

 in unicellular organisms is called conjugation and in multicellular 

 organisms fertilization, and we have seen that its most obvious 

 significance lay in the fact that through it the germ -plasms of two 

 individuals are united. Since, according to our view, this germ- 

 plasm or idioplasm is the bearer of the hereditary tendencies of the 

 organism concerned, the mingling or amphimixis of two germ-plasms 

 brings together the hereditary tendencies of two individuals, and the 

 organism whose development is derived from this mingled germ- 

 plasm must therefore exhibit traits of both parents, and must to 

 a certain extent be made up of the traits of both. This is one result 

 attained by amphimixis. 



But we went further than this, and saw that there is a second 

 result implied in amphimixis, namel}^ that the individual character 

 of the germ-plasm is being continually altered by new combinations 

 of the ids contained in it. We inferred from what I believe to be the 

 demonstrated hypothesis that the germ-plasm is composed of ids, that 

 its reduction to half the orio-inal mass must mean a reduction of the 

 ids to half tlie number, and as the ids contain primary constituents 

 which are individually different, this nuist effect a new arrangement, 

 a new mingling of these individual peculiarities. The reduction of the 

 germ-plasm to half, that is, the diminution of the number of its ids 

 to half, is a phenomenon generally associated with amphimixis, and 



