41 



This germ-plasm according to VVeismann, constitutes the 

 chromatin of the nucleus of the sexual cells ; it is an exceedingly 

 complex living substance, capable of growth, and is of a very 

 high degree of stability, i.e., it is little liable to change. 



The chromosomes formed during the process of cell 

 division from the chromatic substance Weismann designates 

 idants. Idants are made up of a number, varying for each 

 species, of ids. 



Ids are capable of growth and multiplication. Theoreti- 

 cally, one id would suffice for the development of one individual. 

 These ids are made up of determinants, and these again are 

 divided into biophores, the whole combination forming a defi- 

 nite and complex architecture. Of determinants there exists 

 one for every different organ and parts of organs contained in 

 the adult ; their function is, therefore, to determine the char- 

 acter and structure of the organism. The biophores are the 

 ultimate particles of living matter, endowed with the vital force, 

 whatever that may be. 



This brief sketch, incomplete as it is, will enable us the 

 better to understand that which is to follow. 



The first question naturally asked in connection with this 

 theory is : What then is the history of the germ-cells from one 

 generation to the next ? VVeismann's teaching seems to be 

 capable of, at least, two answers; at any rate, two different 

 conclusions may be assumed. One aspect— method {a)~ 

 represents the zygote di\iding into two exactly similar daughter 

 cells, {a) and {b) ; one of these (a) grows and divides," this 

 repeatedly, but the products remain unaltered, i.e., they are 

 all similar to the zygote from which they were produced. In 

 other words, at each division all the characteristics of the 

 zygote are doubled. 



The cell (b) also divides; here, however, doubling does not 

 take place, but exactly the opposite, for the characteristics 

 represented by the determinants are halved in number, and 

 this continually until all the determinants have been distributed, 



