The Nuptial Flight 
further we penetrate into it, the fewer do 
our certitudes become. Darwin, for in- 
stance, to take the man of all men who 
studied it the most methodically and most 
passionately—Darwin, though scarcely con- 
fessing it to himself, loses confidence at 
every step, and retreats before the unex- 
pected and the irreconcilable. Would you 
have before you the nobly humiliating 
spectacle of human genius battling with 
infinite power, you have but to follow 
Darwin’s endeavours to unravel the strange, 
incoherent, inconceivably mysterious laws 
of the sterility and fecundity of hybrids, 
or of the variations of specific and generic 
characters. Scarcely has he formulated a 
principle when numberless exceptions assail 
him; and this very principle, soon com- 
pletely overwhelmed, is glad to find re- 
fuge in some corner, and preserve a shred 
of existence there under the title of an 
exception. 
For the fact is that in hybridity, in 
variability (notably in the simultaneous varia- 
tions known as correlations of growth), in 
instinct, in the processes of vital competition, 
251 
