PLAY AND INSTINCT. 51 



complicated structure* historically handed down, which, 

 indeed, is undeniably the case, but in a more daring 

 hypothesis he attempts to establish the essential elements 

 of this structure: the molecules of germ plasm go in 

 various ways to form Biophores, which determine the 

 cell qualities; f these in turn form Determinants,^ which 

 again find their higher unity in the Ide; * these, again, 

 are grouped in the IdantJ which is identical with the 

 chromosome. 



But this world of minute elements represented by 

 the germ cells is, as I said before, continuous — that is, 

 it is not produced anew in each individual, but persists 

 with great stability throughout the countless successions 

 of related life forms, building up organisms but never 

 exhausted in the process, and not influenced by indi- 

 vidual experience or by heredity. It may be figured as 

 a creeping root, stretching far from the parent stock; 

 single plants rise from it at different points, represented 

 by the individuals of successive generations.* If, then, 

 a material so constituted is the only medium for the 

 operation of heredity, there can be no transmission of 

 acquired characters. 



Weismann's theory taken as a whole is far from uni- 

 versally recognised as established. It has a great num- 

 ber of opponents, of whom I mention only Haeckel,Q 



* Keimplasma, p. 82. 

 f Ibid., p. 53. 



X Ibid., p. 76. 



* Earlier called " Ahnenplasma " by Weismann, ibid., p. 84. 

 | Ibid., p. 90. 



A A. Weismann, Die Bedeutung der sexuellen Fortpflanzung 

 fur die Selectionstheorie, Jena, 1886, p. 20. 



Haeckel, Naturliche Schopfungsgeschichte, 1889, p. 198. An- 

 thropogenic oder Entwickelungsgeschichte des Menschen, 1891, 

 preface. 



