FLUCTUATING VARIATIONS AND THEIR INHERITANCE 5 1 



worm moths. The frequent persistence of tracheae as the only traces of 

 the last venation suggests that possibly the degeneration of the vena- 

 tion starts with a giving up of the structural features acquired latest 

 in the race's and the individual's development (namely the chitinization 

 which occurs about the tracheae as trails) and, proceeding backward 

 through time, repeats the story of the structure's birth — by what might 

 be termed a reversed recapitulation of ancestral stages. 



