86 DOMESTICATED ANIMALS AND PLANTS 
It could not well be otherwise, certainly in so far as vital 
particulars are concerned. If the bill is a little too short or too 
soft to reach the worm as he burrows deeper, then it will be 
promptly lengthened, not in short-billed individuals but in the 
descendants of those with longer bills. If the marking of the 
butterfly is similar to a leaf or a lichen, then those individuals 
in which the resemblance is closest will profit most and the 
similarity will grow closer. If the relations between two species 
happen to be mutually beneficial, then those relations will be still 
better perfected in future generations by the selective process, 
till possibly they may become essential to the existence of one 
or the other, if not of both. 
For example, certain moths have the habit of laying their 
eggs only upon particular plants, then of gathering a pellet of 
pollen off the flowers and storing it near the egg as food for 
the young larva, thereby pollinating the flower.! Some of these 
“fits’’ seem unaccountable except on the basis of intelligence or 
design, but when we remember not only the very low intelligence 
of the moth, but also the fact that she never sees the outcome of 
it all, since she will be dead before her own eggs hatch, the réle 
of intelligence is eliminated. When also we remember that 
some of the best fits are peculiarly fatal to one of its members, we 
rule out design, for nature is not partial as between its creatures. 
Apparent exceptions due to absence of severe selection. The 
fit is often notably bad, as when the moth flies into the candle, 
impelled by an instinct it cannot control,? but to which it 
1See the case of the yucca moth described in “ Principles of Breeding,” 
p- 105, which see also for a general discussion of Instinct, pp. 386-404. 
? Ofttimes the insect’s egg is laid inside the body of another creature, which 
is necessarily fatal, just as the fact that the best temperature and conditions 
for tuberculosis happen to fit alarmingly close with that of cattle (102°) and 
the extremely insanitary way in which many of them are kept in our hot and 
close basement barns. Surely this is not design, nor is it especially beneficent, 
for the tubercle bacillus certainly cannot have interests worth consideration, 
even if we disregard those of our cattle and our own as well. The fit is, never- 
theless, close and complete. 
3 See “ Principles of Breeding,” pp. 394-397, for a discussion of the causes 
of instinctive acts. 
