_Introduction_, p. 555.
_Experiments_, 558. Significance of the facts, 563. The Axolotl rarely
or never undergoes metamorphosis in its native country, 565. North
American Amblystomas, 570. Does the exceptional transformation depend
upon a phyletic advancement of the species? 571. Theoretical bearing
of the case, 574. Differences between Axolotl and Amblystoma, 575.
These are not correlative results of the suppression of the gills,
578. Explanation by reversion, 581. Cases of degeneration to a lower
phyletic stage: Filippi’s sexually mature “_Triton_ larvæ,” 583.
Analogous observations on _Triton_ by Jullien and Schreibers, 591. The
sterility of the artificially produced Amblystomas tells against the
former importance of the transformation, 594. It is not opposed to the
hypothesis of reversion, 596. Attempted explanation of the sterility
from this point of view, 597. Causes which may have induced reversion
in the hypothetical Mexican Amblystomas, 600. Saltness of the water
combined with the drying up of the shores by winds, 604. Consequences
of the reversion hypothesis, 609; Systematic, 609; an addendum to the
“fundamental biogenetic law,” 611; General importance of reversion,
612. _Postscript_; dryness of the air the probable cause of the assumed
reversion of the Amblystoma to the Axolotl, 613. _Addendum_, 622.
=IV.=