202 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Designation of Species A B 
()eOniginal numbers a a> b 
(2) Number lost without imitation. . e— = 
(3) Remainders without imitation . . (a—e) (b—e) 
Shs tie a b 
(4) Number lost with imitation. . . prey Pa oS 
N atb 
be 
a+b a+b 
(5) Remainders with imitation a (4 sane ) b (1 — =H) 
(6) Excess of remainders due 
to imitation, or “abso- 
lute advantage” (3)—(5) 
(7) Ratio of excess to remainders 
without imitation (6): (3), 
=proportional advantage. 
a b e a 
arb a—e | atb ~boe 
é : e 
(8) Ratio of Pacpenianal advan- gaa)’ <a? (1 — +) 
tage of B to proportional ¢- = j=—,——-=7;,, ~+———~< 
; b (b—e) ~ b? e 
advantage of A. (1 ¥) 
It is evident, then, if e be small compared with a and b, that the 
proportional advantage of B is to the proportional advantage of A 
as a? is to b?. If, however, the loss (e) is great compared with a or 
b, the relative gain for the weaker species becomes even greater than 
the ratio of the squares of b and a. 
If it be true, then, that young birds, when they leave the nest, do 
not Possess a directing instinct telling them what they should and 
should not eat, but actually do experiment to some extent upon 
various insects which they meet with, Miiller’s law is amply sufficient 
to account for the numerous cases of mimicry and remarkably close 
resemblances which are found among the species of the Heliconidae 
themselves. 
Unfortunately no direct experiments have ever been made upon 
the feeding-habits of young South American birds, nor have the 
contents of their stomachs been examined, There have been a few 
experiments, however, which seem to support the idea that some 
animals do learn to associate an agreeable or disagreeable taste with 
the coloration and appearance of their prey. It is well known that 
Weismann (782, p. 336-339) found that the black and yellow 
larvae of Euchelia jacobaeae were refused by the green lizard of 
Europe. He then introduced some young caterpillars of Lasiocampa 
