g8 THE FIRST PRINCIPLES OF HEREDITY 



ritual purposes, as in circumcision, etc., no permanent 

 effect has resulted. Experiments made with the same 

 object in view all proved futile. Weismann cut off the 

 tails of mice for generations without achieving so much as 

 a shortening of the tail, not to speak of a complete loss of 

 it. The only experiments in favour of the positive assertion 

 are the well-known ones by Brown-Sequard on guinea-pigs. 

 By severing certain nervous tracts in the animals, he pro- 

 duced pathological changes, such as epilepsy, paralysis, 

 etc., which in a small percentage of the cases reappeared in 

 the offspring. These experiments have been repeated with 

 by no means the same uniform result. Furthermore, 

 Brown-Sequard's own cases seem to many scientists not 

 sufficiently distinctive to afford unequivocal proof. As 

 the matter at present stands, mutilations and the like 

 form the weakest point of the armoury of the upholders of 

 the inheritance of acquired characters. 



(c) CONGENITAL TRAITS. 



There is a good deal of confusion in the average mind 

 between congenital traits and inherited characters. The 

 term " congenital " is taken by many to be identical with 

 " inherited." But a character may be congenital i.e., be in 

 evidence at birth and yet not inherited. As each being 

 starts its independent existence from the moment the 

 parental germ-cells unite in the act of fertilization, any- 

 thing which happens to this being from that moment 

 onward by influences external to it must be reckoned as an 

 acquired character, the only difference being that con- 

 genital modifications are acquirements occurring in utero 

 before the actual birth. The mere act of birth cannot, and 

 does not, alter the organic relationship between body and 

 germ cells of the individual. In fact, we may have inborn 

 traits which are blastogenic, due to arrested development 

 of the germ, as hare-lip and other malformations ; and, on 

 the other hand, defects, malnutrition, etc., due to dis- 



