ACQUIRED CHARACTERS 29 



able. Finally, we have the direct experimental evidence of 

 Weismann, who cut off the tails of mice for nineteen genera- 

 tions in succession without however observing any inheri- 

 tance of the mutilation. We have also the evidence furnished 

 by long-continued mutilations practiced by man upon his 

 own person, such for example as tatooing and circumcision. 

 The effects of such mutilations, as is well known, are not in- 

 herited in the slightest degree. 



Notwithstanding all this negative evidence, Semon, who 

 like a drowning man catches at every straw, cites Kammerer 

 as having recently shown that a soft-bodied marine animal 

 (Ciona, an ascidian) after its siphons are cut off regenerates 

 new ones longer than normal, and he maintains that the 

 young of such animals have siphons of abnormal length. In 

 view of all the negative evidence furnished by other animals 

 this case, as yet incompletely published, seems highly im- 

 probable. The unsupported claim throws more light upon 

 the credibility of Kammerer as a witness (and he has brought 

 forward many cases in recent years) than upon the general 

 question of the inheritance of mutilations. 



2. Congenital diseases. Cases of disease acquired by a 

 parent and by him transmitted to his offspring are frequently 

 reported. But all these cases are capable of other explana- 

 tions than that of inheritance of an acquired character. 



(a) In some cases a disease-producing organism may be 

 present in the body of the parent and may pass directly into 

 the reproductive cell. Thus in silkmoths, the organism 

 which causes "pebrine" is transmitted as an infection within 

 the egg, as Pasteur showed. The same is true of Texas fever 

 in cattle. This disease is caused by a protozoon which is 

 introduced into the blood of cattle by a tick which harbors 

 the disease. The protozoan parasite is present in the egg-cell 

 of the tick, so that the young tick which develops out of such 

 infected eggs cannot fail to contain the parasite; but the 

 disease is no more inherited than a grain of sand placed within 

 the egg would be inherited. In a similar way in man syphilis 

 may be transmitted, but it is in no true sense inherited. Yet 



