Table 1. Symbols.

c	Proportionality between stress at T2 and stress at T1 in generalized model
f	Peak apical tension during contraction
h	Duration of apical tension during contraction
J	Compliance: relates strain and stress as a function of time since stress application
k	Hypothetical constant of proportionality between peak apical tension and stress driving blastopore closure
RCP	Relative duration of blastopore closure to progression of involution: tC/tP
t	Clock time
T	Temperature
tC	Time for blastopore closure
tP	Time for dorsal-ventral progression of involution
w	Slope of stress in ramp model
α	Proportionality between developmental time and clock time in generalized model
β	Exponent that determines time dependence of compliance
ε	Strain (Ln[L/L0), a non-dimensional measure of deformation
σ	Stress (force/area)
τ	Developmental time in generalized model (Model 1)