xliv MEMOIR. 
selves, and have juices which exhale a powerful scent, so that when 
one kills them by pinching the body, the liquid that exudes stains 
the fingers yellow, and leaves an odour that can only be removed 
by repeated washings.” * 
2. The frequency and exactness of mimetic analogies in insects 
is explained by their having “perhaps attained a higher degree 
of specialisation, after their type, than most other classes, as 
seems to be shown by the perfection of their adaptive structures 
and instincts.” Their being more numerous and striking in 
tropical than in temperate countries is perhaps attributable to 
the more active competitive life,’ and immense fertility, “with 
more rapid succession of their generations in hot than in cold 
countries.” f 
Objections have been advanced against Bates’s explanation of 
mimicry, chiefly by naturalists whose conservatism retards their 
application of the theory of natural selection to every part of every 
organism ; or whose pusillanimity causes them to wear a livery 
mimetic of old forms of belief, which enables them to pass muster 
with the orthodox. 
To the objection that mimicry is a special endowment for the 
protection of the animal, the answer that there are gradations of 
mimetic analogies is sufficient. To the objection that similar con- 
ditions produce the resemblances between the mimicked and the 
mimicker, the answer is that similar conditions act only on a small 
proportion of organisms, the mimetic analogies being limited to a 
few groups. To the objection that mimicry is produced by re- 
version to ancestral types, the answer is that the imitation is only 
in external and visible characters, and that the argument does not 
account for the mimickers and the mimicked tenanting the same 
areas. 
The basis of mimetic analogies lies in the origination of some 
slight variation in the mimicker which tends in the direction of 
likeness to the mimicked. Upon this variation natural selection 
operates. 
The reception given to Bates’s paper was most gratifying to 
him. Darwin heard it, and, on its publication, wrote as follows :{— 
* Darwinism, p. 234, and cf Mr. Poulton’s paper on ‘‘The Experimental Proof of 
the Protective Value of Colour and Markings in Insects,” especially Table, p. 262. Proc. 
Zool. Soc., March 1887. 
+ Upon this, see Darwin’s letter next page, 
t This letter has been printed in the Zzfe and Letters, ii., 391. 
