ORGANIC EVOLUTION — THE FACTORS 131 



acquired an epileptic habit, such that a pinch on the 

 neck would produce a fit, inherited an epileptic habit 

 of the kind. It has, indeed, been since alleged that 

 guinea-pigs tend to epUepsy, and that phenomena of 

 the kind described occur where there have been no 

 antecedents Hke those in Brown-Sequard's case. But 

 considering the improbability that the phenomena 

 observed by him happened to be nothing more than 

 phenomena which occasionally arise naturally, we may, 

 until there is good proof to the contrary, assign some 

 value to his results." — The Factors of Evolution. 

 Williams and Norgate: 1887. 



But if it is true that epilepsy usually supervenes in 

 guinea-pigs when the sciatic is severed, and that this 

 acquired epilepsy is generally or even occasionally in- 

 herited by the ofifepring, there appears to be strong 

 grounds for supposing that the acquired variation in 

 this case is transmissible. But before we could posi- 

 tively decide as to this we should have to still further 

 extend our inquiry. 



But here the reader must be reminded of that which 

 was insisted on in a former page, namely, that in the 

 last analysis all inborn variations in any organism must 

 be due to acquired variations in the germ cell from 

 which it arose. He must remember that it is not 

 denied that a force acting on an organism may produce 

 changes in its germ cells, and consequently in the de- 

 scendant organisms; but that it is denied that the 

 changes produced in the germ cell are usually such 

 that in consequence of them they tend to grow into 

 organisms in which appear changes similar to the 

 changes produced by the force in the parent organism. 

 He must remember that it is not asserted that a force 

 acting on an organism cannot produce such a change in 

 the germ as will cause the organism into which it 

 develops to exhibit a variation similar to the variation 



