68 THE EVOLUTION THEORY 



support the Lamarckian principle. One could only say: Certain 

 injuries to the nervous system give rise secondarily in guinea-pigs 

 to morbid phenomena like epilepsy, and all sorts of functional dis- 

 turbances of the nervous system often appear in the next generation, 

 including in rare cases even the phenomena of epileptic convulsions. 

 That this is a case of the transmission of an acquired anatomical 

 modification brought about by the injury is not only unproved, but 

 is decidedly negatived, for the injuries themselves are never trans- 

 mitted. Thus what is transmitted must be quite different from what 

 was acquired, for no one has ever detected in the offspring the lesion of 

 the nerve-trunk which was cut through in the parent, or any other 

 result except the disease to which the original injury gives rise. 

 Moreover, the inheritance of these morbid phenomena has been again 

 brought into dispute quite recently owing to the investigations of such 

 experts in nervous diseases as Sommer and Binswanger, and the cor- 

 rectness of Brown-Sequard's results, which have dragged through the 

 literature of the subject for so long, has been emphatically denied^. 



Clearly formulated problems, like that of the inheritance of 

 acquired characters, should not be confused by bringing into them 

 phenomena Avhose causes are quite unknown. What do we know of 

 the real causes of those central brain-irritations Avhich give rise to the 

 phenomena of epilepsy ? It is certain enough that there are diseases 

 which are acquired and are yet ' inherited,' but that has nothing to 

 do with the Lamarckian principle, because it is a question of infection 

 of the germ, not of a definite variation in the constitution of the 

 germ. We know this with certainty in regard to the so-called 

 Pebrine, the silkworm disease which wrought such devastation in 

 its time ; the germs of the pebrine organism have been demonstrated 

 in the egg of the silk-moth ; they multiply, not at once but later, in the 

 young caterpillar, and it is the half-grown caterpillar, or even the 

 moth, that succumbs to the disease. 



Whether in this case also the disease germs are transmitted 

 through the male sex-cells is not proved, as far as I am aware, but 

 that this can happen is shown by the transmission of syphilis from 

 father to child. That in this case, also, the exciting cause of the 

 disease is a micro-organism cannot be doubted, although it has not yet 

 been proved. Thus even the minute spermatozoon of Man can contain 

 microbes, and transmit them to the germ of a new individual. 



This discussion of scientific questions ought not to be brought 

 down to the level of a play upon words, by bringing forward cases 

 like the above as evidence for the inheritance of ' acquired characters,' 



^ See H. E. Ziegler's report in Zool CentraWIalt, 1900, Nos. 12 jind 13. 



