_Larva and Imago vary in Structure independently of each other_, p. 401.
Dimorphism of one stage only, 402. Independent variability of the
stages (heterochronic variability), 403. Constancy and variability are
not inherent properties of certain forms of marking, 407. Heterochronic
variability is not explained by assuming a phyletic vital force,
410. Rarity of greater variability in pupæ. Greater variability more
common among caterpillars than among the imagines. Causes of this
phenomenon, 412. Apparent independent variability of the single larval
stages. Waves of variability, 416. _Saturnia Carpini_ an instance of
_secondary_ variability, 419. Causes of the exact correlation between
the larval stages and its absence between the larva and imago, 429.