THE MULTICELLULAR ORGANISM. 1 49 



by means of the seed, of the physical and mental characteristics of the 

 father, affect all the questions which the human mind has ever raised in 

 regard to existence." — Rudolph Viechow (1848). 



The discovery that every human being at the beginning 

 of his existence is a simple cell, that this egg-cell is essen- 

 tially similar to those of other Mammals, and that the 

 forms arising during the evolution of this cell in Man and 

 in the other higher Mammals, are at first similar, — supplies 

 a basis from which we may trace the further processes of 

 evolution. In the first place we have convinced ourselves 

 of a fact which is of great importance to the empiric side 

 of the history of development, relating to those ontogenetic 

 facts which can be directly traced by means of the micro- 

 scope ; and this fact is that in Man as well as in other 

 animals the developed many-celled organism with all its 

 various organs proceeds from a simple cell. Secondly, as 

 regards the phylogenetic side of the question, the specu- 

 lative part of the History of Human Development, which 

 is based on those facts, we have reached the conclusion 

 that the original ancestral form of Man as of the other 

 animals was a one-celled organism. The whole difficult 

 problem of the History of Evolution is thus now reduced 

 to the simple question : " How has the complex many-celled 

 organism arisen from the simple one-celled form ? By what 

 natural process has the simple cell been transformed into 

 that complex life-apparatus with all its various organs, the 

 apparently rational and purposive construction of which we 

 admire in the developed body ? " 



Turning now to answer this question, we must bear in 

 mind the view to which we have already alluded, that the 

 many-celled organism is ordered and constituted on the 



