Transcriber's Notes:
Changed "vestigal" to "vestigial" on page 578: vestigal-winged flies.
Changed "inmature" to "immature" in Table 2: nematodes that were inmature.
Changed "auomatically" to "automatically" on page 582: not auomatically invalid.
Changed "Syzmanski" to "Szymanski" in Literature Cited on page 585.