32 HEREDITY AND SELECTION IN SOCIOLOGY 



influence of the suiroiuiding protoplasm ? Determinants must 

 be units capable of assimilation and reproduction. 



Determinants must also be autonomous— that is to say, a 

 determinant or group of determinants must be able to modify 

 a given determinate of the organism without modifying the 

 whole. The case of those individuals who have one small tuft 

 of white hair amongst a mass of dark hair is an example of this. 

 The determinant of this tuft of white hair may be eliminated 

 in the course of generations, and the determinate — the tuft of 

 white hair itself— disappears accordingly from the soma; but 

 the rest of the organism is not in any way affected by this 

 change. 



If the determinants, during the process of development, resolve 

 themselves into their component units, the biophors, and pene- 

 trate in this way into the cells which they are to determine, 

 then the id must have the faculty of dividing into similar, and 

 also into dissimilar, parts ; it must be able to produce daughter 

 ids which are homodynamic, and other daughter ids which are 

 heterodynamic — that is to say, it must be able to produce ids 

 containing determinants differing in character. The first type 

 of id division is called integral division ; the second type is called 

 differential. A difierential division of the id is not directly 

 demonstrable ; we become aware of it only in its somatic results, 

 in the different role which different cells play in the ontogenesis. 

 For instance, when two sister cells in the embryo give rise, one 

 to the endoderm, the other to the ectoderm, we must conclude 

 that the primitive cell has differentiated its germinal substance, 

 and that in the division that germinal substance has been 

 divided in a dissimilar fashion between the daughter cells, one 

 of which produces the ectoderm, from which the epidermis and 

 the nervous system are developed, while the other produces the 

 endoderm, from which the food-canal and its outgrowths arise. 

 Differential karyckinesis will take place in every case in which 

 a cell is divided into two daughter cells having a dissimilar or 



