Conclusion 71 



met and thereby grow, and then multiply by division, 

 two new pangens, like the original one, usually originat- 

 ing at each cleavage. Deviations from this rule form a 

 starting point for the origin of varieties and species. 



At each cell-division every kind of pangen present is, 

 as a rule, transmitted to the two daughter-cells. What 

 combination of circumstances is the condition of this, and 

 what relation is established by the practically uniform 

 multiplication of the various pangens of an individual, 

 we do not know. 



The pangens, in smaller and larger groups must stand 

 in such a relation to each other that the members of one 

 group, as a rule, become active at the same time.*^ 



All these conclusions follow naturally when we try 

 to connect the fundamental thought with the known 

 phenomena of heredity and variability. 



The whole import of this fundamental idea will, I 

 believe, be made most clear by briefly grouping now the 

 most important advantages of the hypothesis in answering 

 some great biological questions. For entire large groups 

 of phenomena are made comprehensible to us in a simple 

 manner, and this without any ancillary hypothesis, by a 

 mere consideration of the ever changing relative quan- 

 tities in which the pangens must occur, according to the 

 nature and age of the cells. In the main these advan- 

 tages have already been pointed out by Darwin. 



According to Darwin's idea, the phenomena of hered- 

 ity evidently depend on the fact that the living matter 

 of the child is built up of the same pangens as those 

 of its parents. If the pangens of the father predominate 

 in the germ, the child will resemble him more than the 



^'Darwin called these groups "compound gemmules.' Loc. cit. 

 2: 366. New York. 1900. 



