Weismann s theory of Heredity (1891). 73 



genetically, or without admixture of germ-plasms in 

 any previous act of sexual fertilization, do not exhibit 

 congenital variations. 



Taking, then, these three lines of verification separ- 

 ately, none of them need detain us long. For although 

 the fact of the migration of germ-cells becomes one of 

 great interest in relation to Weismann's theory after 

 the theory has been accepted, the fact in itself does not 

 furnish any evidence in support of the theory. In 

 the first place, it tends equally well to support Galton's 

 theory of stirp ; and therefore does not lend any 

 special countenance to the theory of germ-plasm— or 

 the theory that there cannot now be, and never can 

 have been, any communication at all between the 

 plasm of the germ and that of the soma. In the 

 second place, the fact of such migration is not incom- 

 patible even with the theory of pangenesis, or the 

 theory which supposes such a communication to be 

 extremely intimate. There may be many other 

 reasons for this migration of germ-cells besides the 

 one which Weismann's theory supposes. For example, 

 the principle of physiological economy may very 

 well have determined that it is better to continue for 

 reproductive purposes the use of cells which have 

 already been specialized and set apart for the execu- 

 tion of those purposes, than to discard these cells 

 and transform others into a kind fitted to replace 

 them. Even the theory of pangenesis requires to 

 assume a very high degree of specialization on the 

 part of germ -cells ; and as it is the fact of such 

 specialization alone which is proved by Weismann's 

 observations, I do not see that it constitutes any 

 criterion between his theory of heredity and that of 



