THE GENERAL SIGNIFICANCE OF AMPHIMIXIS 225^ 



assumed organisms have not yet been observed with certainty. 

 Perhaps they all lie below the limits of visibility, and then we could 

 never do more than tuppom that plastogamic processes occur among 

 them. Logically and purely theoretically we may buppote that amphi- 

 mixis occurred first between the plasmic bodies of non-nucleated 

 Monera, then between the cell-bodies of true cells, and finally between 

 the nuclei of cells. 



Let us hold fast to what we have found to be probable, namely, 

 that the fusion of individually difterent simple organisms must or may 

 bring about a direct advantage— a stimulation of the metabolism, and 

 at the same time an improvement of the constitution in different 

 directions, and let us go on to the consideration of cell-fusion com- 

 bined with nuclear fusion, or complete amphimixis. In this something 

 is added which we can recognize as an important advantage, namely, 

 the combination of two hereditary substances, and thus the union 

 of two variation-complexes which, according to our view, is necessary 

 if transformation of species is to take place. In mere plastogamy 

 such a union of two hereditary masses could only take place in Monera, 

 not in nucleated organisms. If then there are really unicellular 

 organisms which exhibit plastogamy without karyogamy (certain 

 Foraminifera), we have a further proof that these processes of plasmic 

 fusion imply direct advantage, which is distinct from the indirect 

 advantage lying in the mingling of two different hereditary con- 

 tributions, since in these cases of plastogamy there is no demonstrable 

 mingling of hereditary bodies, no karyogamy. 



But as soon as karyogamy or nuclear fusion was associated with 

 mere plastogamy, complete amphimixis could never be lost again, 

 because it alone made it possible that there should be harmonious 

 transformation and adaptation in organisms which were becoming 

 ever more complex; the primary effect of the mingling would be more 

 and more transcended, since, without amphimixis, transmutation with 

 harmonious adaptation in all directions would be less and less possible 

 as organisms became more complex in structure. I have already 

 referred to the manifold details in the structure and development 

 of the lowest organisms which make this conclusion appear luminous 

 to us, but we can also infer the necessity for an unceasingly active 

 selection, from a quite different set of facts, namely, from what we 

 know of rudimentary organs in Man. 



We may regard Mankind as a species which has its local races 



and sub-races, but which is fixed in its essential characters, and only 



fluctuates hither and thither in individual variation in each sub-race, 



just like any other modern mammal, such as the marmot or the hare. 



ir. Q 



