MATERIAL CAUSES OP HEREDITY. 1 99 



of the maternal organism, and, no less mysterious, that at 

 the same time the essential qualities of the paternal 

 organism are transferred to the offspring by means of the 

 male sperm, which fructifies the egg-cell by means of a 

 viscid substance in which minute thread-like ceUs or zoo- 

 sperms move about. But as soon as we compare the con- 

 nected stages of the different kinds of propagation, in whicli 

 the produced organism separates itself more and more as a 

 distinct growth from the parental individual, and more or 

 less early enters upon its independent career; as soon as 

 we consider, at the same time, that the growth and develop- 

 ment of every higher organism only depends upon the 

 increase of the cells composing it — that is, upon their 

 simple propagation by division — it becomes quite evident 

 that all these remarkable processes belong to one series. 



The life of every organic individual is nothing but a 

 connected chain of very complicated material phenomena 

 of motion. These motions must be considered as chano^es 

 in the position and combination of the molecules, that is, 

 of the smallest particles of animated matter (of atoms 

 placed together in the most varied manner). The specific, 

 definite tendency of these orderly, continuous, and inherent 

 motions of life depends, in every organism, upon the 

 chemical mingling of the albuminous generative matter to 

 which it owes its origin. In man, as in the case of the 

 higher animals which propagate themselves in a sexual 

 manner, the individual vital motion commences at the 

 moment in which the egg-cell is fructified by the spermatic 

 filaments of the seed, in which process both generative 

 Hubstances actually mix; and here the tendency of the 

 vital motion is determined by the specific, or more 



