94 SCIENCE PROGRESS 



extracted from his Evolution Theory, English Translation 1904, 

 show his opinions at that date, and I believe up to the present 

 time : 



" Haycraft also finds the significance of amphigony simply 

 in the equalising or neutralising of individual differences which 

 it effects. Quetelet and Galton have attempted to show that 

 intercrossing leads to a mean which then remains constant. 

 Haycraft supposes that a species can only remain constant if 

 its individuals are being continually intercrossed, and that 

 otherwise they would diverge and take different forms, because 

 the ' protoplasm ' has within itself the tendency to continual 

 variation " . . . " the fundamental idea, that amphigony is an 

 essential factor in the maintenance ... of species, is un- 

 doubtedly sound . . . but we cannot simply suppose that 

 amphigony and variation are, so to speak, antipodal forces, 

 the former of which secures the constancy of species, the latter 

 its transformation. In my opinion, at all events, there is no 

 such thing as a ' tendency ' of protoplasm to vary, although 

 there is a constant fluctuation of the characters — dependent 

 on the imperfect equality of the external influences, especially 

 of nutrition." Thus the " real root of variation " is the same 

 as that alleged by Darwin. Nevertheless the stone here 

 rejected by the builder may yet become the head-stone of the 

 corner. It may be that sex and variation are " antipodal 

 forces," in that sex, by ensuring the communication of varia- 

 tions among large numbers of individuals, may check the 

 unlimited divergence that would otherwise ensue. Without 

 sex every individual line of living creatures tends to diverge, 

 like a tree growing into divergent branches; by sex individual 

 lines are bound together like intercrossing threads of a net- 

 work, and divergence occurs in the large communities called 

 species only in proportion as intercrossing is prevented or is 

 rare. Haycraft's " supposition " is really nothing but a fact. If 

 a species of animal, spreading over two areas, is kept from 

 free intercrossing by an intervening sea, or a beetle by a 

 mountain range, it invariably diverges into varieties, and 

 ultimately into species and genera. But as to the "tendency 

 of protoplasm to vary," this would be better expressed as the 

 impossibility of securing an exactly equal division of the matter 

 of a mother-cell, or of any part of a mother-cell, between the 

 two daughter-cells whenever fission occurs. In a subsequent 



