1 82 THE EVOLUTION OF MAN. 



sperm-cell ; (3) the substance of the maternal germ-vesicle 

 (kernel-substance or nuclein of the egg-cell) ; and (4) the 

 substance of the paternal sperm-kernel (kernel-substance or 

 nuclein of the sperm-cell). From the mixture of the two 

 former substances (1, 2) the protoplasm of the parent-cell 

 (Fig. 21, p) seems to originate ; from the mixture of the two 

 forms (3, 4) the parent-kernel (cytococcus) seems to origin- 

 ate (Fig. 21, ft). 52 



The parent-cell (cytula, Fig. 21), which was formerly 

 regarded as merely the "fertilized egg-cell," differs very 

 essentially, therefore, from the original egg-cell, both in 

 point of form (morphologically), and in point of composition 

 (chemically^ and lastly, also in point of vital qualities 

 (physiologically). Its origin is partly paternal, partly 

 maternal; we need not, therefore, be surprised, when we 

 see that the child, which develops from this parent-cell, 

 inherits individual qualities from both parents. 53 



The vital activities of each cell form a sum of mechani- 

 cal processes, which depend radically on movements of the 

 smallest "life particles," the molecules of the living sub- 

 stance. If we call this active substance the Plasson, and 

 the molecules the Plastidules, we may say that the indi- 

 vidual physiological character of each cell depends on the 

 molecular movements of its plastidules. The plastidule 

 movements of the cytula are therefore the resultant of the 

 united plastidule movements of the female egg-cell and of 

 the male sperm-cell. If we regard the two latter as the 

 sides of the parallelogram of forces, then the plastidule 

 movement of the cytula is the diagonal. In my work on 

 the " Perigenesis of Plastidules " (1876), I have explained 

 the important bearing of this conception in explanation of 

 the elementary processes of evolution. 



