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. 



13 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 Ageronia 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. 



14 1 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. — Ed.] 



