190 Inheritance of Acquired Characters 
modifications of it, and so the transmission of acquired 
characters is not excluded.” °° 
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therefore withdrawn from natural selection, the minus 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. 
**°Nugbaum: Zur Differenzierung des Geschlechts im Tierreich. 
Arch. f. mikr. Anat. Bd. 18. Erstes Heft. Bonn. Cohen. 1880. 
P. 113. 
