324 SIGNIFICANCE OF SEXUAL REPRODUCTION [V. 



which are morphologicall}?- and physiologically equivalent \' 

 Just as a sensory nerve produces the sensation of pain under 

 various stimuli, such as pressure, inflammation, infection with 

 the poison of malaria, etc., so various stimuli might cause the 

 nervous centres concerned to develope the convulsive attack 

 which, together with its after-effects, we call epilepsy. In 

 Westphal's case, such a stimulus would be given by a powerful 

 mechanical shock, in Brown-Sequard's experiments, by the 

 penetration of microbes. 



However, quite apart from the question of the validity of 

 this suggestion, we can form no conception as to the means by 

 which an acquired morphological change in certain nerve-cells 

 — a change which is not anatomical, and probably not even 

 microscopical, but purely molecular in nature — can be possibly 

 transferred to the germ-cells : for this ought to take place in 

 such a manner as to produce in their minute molecular structure 

 a change which, after fertilization and development into a new 

 individual, would lead to the reproduction of the same epilep- 

 togenic molecular structure of the nervous elements in the gre}' 

 centres of the pons and medulla oblongata as was acquired by 

 the parent. How is it possible for all this to happen ? What 

 substance could cause such a change in the resulting offspring 

 after having been transferred to the ^gg or sperm-cell ? Per- 

 haps Darwin's gemmules may be suggested ; but each gem- 

 mule represents a cell, while here we have to do with mole- 

 cules or groups of molecules. We must therefore assume the 

 existence of a special gemmule for each group of molecules, 

 and thus the innumerable gemmules of Darwin's theory must 

 be imagined as increased by many millions. But if we 

 suppose that the theory of pangenesis is right, and that the 

 gemmules really circulate in the body, accompanied by other 

 gemmules from the diseased parts of the brain, and that some 

 of these latter pass into the germ-cells of the individual, — to 

 what strange results would the further pursuit of this idea 

 lead ? What an incomprehensible number of gemmules must 

 meet in a single sperm- or germ-cell, if each of them is to 

 contain a representative of every molecule or group of mole- 

 cules which has formed part of the body at each period of 

 ontogen3^ And yet such is the unavoidable consequence of 



^ 1. c, p. 269. 



