through alterations in the germ plasm, and not directly 

 through changes in the body-cells "^ Besides, Weismann 

 adopts and extends the principle of Natural Selection of 

 Darwin by the conception of Germinal Selection. He re- 

 presents a "struggle among the determining elements of the ' 

 germ-cell ' s organization. 1 1 is at least conceivable that the 

 stronger "determinants," i.e., the particles embodying the 



Fig. 9.— AUGUST WEISMANN 



rudiments of certain qualities, will make more of the food 

 supply than those which are weaker, and that a selective 

 process will ensue" (Thomson). 



Panmixia. — Weismann attempted to explain how use- 

 less organs degenerate under the operation of Natural Se- 

 lection by his theory of Panmixia. When under new con- 

 ditions certain organs become useless natural selection 

 ceases to operate, and the individual will no longer be at a 

 disadvantage and therefore will survive. The crossing of 



(1) — The idea of Germinal Continuity was suggested also by Owen 

 (1849). Haeckel (1874), Rauber (1S79), Galton, Jager, Brooks 

 (1876), and Nussbaum. 



35 



