270 Proceedings of the Royal Physical Society. 
But we are more interested in Hartog’s corroboration of 
the general idea. “I accept then,” he says, “one main 
thesis of the ‘Evolution of Sex, that male and female are 
distinguished by their respective temperaments,” or, as we 
should say, by their contrasted metabolic ratios. 
9, WEISMANN’S THEORY OF AMPHIMIXIS.—In 1891, Professor 
Weismann, whose influence upon modern biology has already 
been of the highest importance, published an essay entitled 
“ Amphimixis oder die Vermischung der Individuen,” the 
conclusions of which, if ultimately established, are bound to 
introduce fundamental changes in our conception of sexual 
reproduction. Weismann’s essay has been translated in the 
second English edition(of his collected papers, where it bears the 
title “ Amphimixis, or the Essential Meaning of Conjugation 
and Sexual Reproduction.” As the essay is one of consider- 
able length and complexity, it may be convenient to separate 
the main conclusions from the detailed discussions which 
they involve. 
His main object is “to express, more fully than before, 
the thought that the process which we are accustomed to 
regard as reproduction, is not reproduction only, but contains 
something swi generis, something which may be connected 
with reproduction proper, and in the higher plants and 
animals zs so connected, but which is entirely separate in 
the lower organisms.” This “something” is amphimixis, or 
the mingling of the different hereditary tendencies of two 
individuals. | 
Weismann maintains that the progress of science, e.g., what 
we have come to know about parthenogenesis, maturation, 
the parallel processes of oogenesis and spermatogenesis, the 
behaviour of the chromatin rods, etc., is in favour of his con- 
clusion that fertilisation is not a ‘‘vitalisation of the germ,” 
nor a “rejuvenescence of vital processes,” but that it “has no 
significance, except in the union in the single offspring of 
the hereditary substance from two individuals.” He believes 
that the prevalent conception of fertilisation as a renewal 
of life is bound up with a lingering credence in a “vital 
force.” He completely rejects the idea of the interaction of 
two opposed sexual cells of different qualities, or of any 
