REPRODUCTION AND HEREDITY 325 



maternal nucleus-loops, but each carries the 4 rudiments ' of the 

 parents in any conceivable combination. Though now the 

 parental chromosomes are in the case of the germ-cell formations 

 divided by maturity-division each of them will still be composed 

 of * primary constituents ' of a double lineage. Accordingly, the 

 descendants must exhibit the character of both parents in an 

 entirely different combination. 



In the majority of cases the paternal and maternal qualities 

 will on an average balance each other ; in many individuals the 

 influence of the father will be prevalent, in others that of the 

 mother, and sometimes it may even occur that the type of one 

 of the parents is almost entirely suppressed. 



In the cases of Mendelism the proportions are somewhat 

 different ; there we may conceive that the ' rudiments ' of the 

 ' splitting characters ' have gradually become differentiated so 

 much that they may no longer be exchanged one for another, but 

 that all ' rudiments ' of the relevant character always meet 

 again in their definite nucleus-loops. However different the 

 combinations of the other rudiments may be, as regards the 

 ' Mendelian rudiments,' always pure sex-cells are formed. 

 Formally this hypothesis suffices for explaining all the manifold 

 phenomena of heredity, but how far it will be possible to support 

 it by facts, or what modifications it will have to undergo, only 

 the future can say. 



Our excursions into the region of biology have led us along 

 many sinuous paths, across luxuriant fields and dry deserts, to 

 the high summits of mountains, and through narrow ravines. 

 We have seen what the human mind has achieved in restless 

 labour, and how Nature has been forced to yield up many profound 

 secrets, but our wanderings have also led us to many locked 

 doors at which we knocked in vain for admission. However 

 great the treasures of knowledge raised in the past and the 

 present, still greater treasures await discovery by future genera- 

 tions. Moreover, who will say that much which is to-day valued 

 as gold may not be rejected as dross by posterity, and much that 

 is regarded to-day as a secure possession of science may not 

 have crumbled away in a few generations ? 



Der steht wohl niedrig in der Toren Mitte, 

 Wer blindlings hat das Ja und Nein gefunden, 

 Nicht unterscheidet, ob es Deutung litte. 



