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554 THE ZOOLOGIST. 
under favourable circumstances, is probably to reduce the number of 
enemies, this success being compensated, however, by the more per- __ 
sistent attacks of certain special enemies—the result being the same as 
in the cryptic colouring, namely, to keep up the average number of 
individuals. 
* Darwin remarks on the sound made by this species (‘ Voyage of 
the Beagle’), which he witnessed during his travels in South America. 
He believed that the sound was of sexual significance, and in his essay 
on sexual selection compared it to that made by the males of Halias 
prasinana during courtship—a sound which I have myself once heard. 
The display or exercise of secondary sexual characters is probably often 
a danger to the individual, although I fail to see how it is possible 
to argue from this that the cryptic colouring and attitudes of other 
phases of life are thereby rendered inoperative and valueless. The 
sound-producing time is one of high activity and rapid movement in 
both the species of Lepidoptera mentioned ; in the case of the common 
English moth it is indulged in so rarely, that comparatively few 
naturalists have ever heard it, while in dAgeronia it is not likely to be 
produced during more than a very small proportion of the life of the 
male. As to its cryptic colouring and, of even more importance, the 
corresponding instinctive attitudes and movements, Darwin made 
special remark in the volume already mentioned. 
* T have noticed the same thing in North America. Not only was 
the distance very difficult to estimate, but the direction from which the 
sound came equally hard to trace. 
[In closing this discussion, which has now extended beyond the limited 
space of ‘ The Zoologist,’ as writer of the incriminated “ Suggestions,” I ought 
perhaps to make some rejoinder. This is unnecessary to my friend Mr. 
Marshall's objections, as they principally express an ably stated difference of 
opinion, and I have merely added footnotes to make his quotations from my 
suggestions a little more ample and representative. Prof. Poulton, in for- 
warding his ‘‘ Notes,’ with his usual fairness, wrote: ‘*‘ My remarks are more 
of a reinforcement of Marshall’s arguments than a direct answer to your 
paper, which I have not seen. I expect, however, from Marshall’s MS., that 
they do affect the drift of your argument, and are therefore in the nature of a 
reply.” This statement of course disarms any rejoinder. Besides which a 
comparison of Poulton’s notes to Marshall’s opinions also discloses a diversity 
of view, though the first named states he entirely agrees with Mr. Marshall’s 
argument. Thus Mr. Marshall writes (ante, p. 538), “It is possible no 
evolutionist would deny,” and Prof. Poulton to this adds the note, ‘‘ Probably 
most evolutionists would hesitate before committing themselves to such a 
conclusion.” Again, they both differ as to the active mimicry of the Fox 
(cf, pp. 541, 552). A triangular discussion is therefore out of the question, 
and we may continue to differ in opinion and search together for facts.— Ep. } 
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