190 Inheritance of Acquired Characters 



modifications of it, and so the transmission of acquired 

 characters is not excluded." 15 



After thus having brought forward and refuted the 

 four principal arguments adduced by Weismann against 

 the Lamarckian theory, we must now examine the value 

 of the corollaries and subsidiary theories which this 

 investigator devised to defend his doctrine from the mani- 

 fold objections which were brought forward from all 

 sides to show its inadmissability. 



Panmixia presents itself as the first subsidiary 

 theory. It has entirely succumbed. It was devised by 

 Weismann to explain the progressive phyletic atrophy of 

 the organs which have become useless, and rests on the 

 supposition that as soon as the fortuitous variation of a 

 certain organ has become useless for the species, and is 

 therefore withdrawn from natural selection, the minus 

 variations which this organ would chance to present in 

 certain individuals would no longer cause the disappear- 

 ance of these latter in the struggle for existence. The 

 survival of organisms with such minus variations and 

 their sexual union with individuals which still preserve 

 the organ in its original state would lead gradually to 

 the degeneration, progressive atrophy and final disappear- 

 ance of the organ. 



Spencer, nevertheless, rightly draws attention to the 

 fact that the appearance of plus variations is just as 

 probable as that of minus variations, and therefore pan- 

 mixia is not at all capable of explaining by itself this 

 progressive and continuous degeneration of useless 

 organs. 



1BO Nubaum: Zur Differenzierung des Geschlechts im Tierreich. 

 Arch. f. mikr. Anat, Bd. 18. Erstes Heft. Bonn. Cohen. 1880. 

 P. 113- 



