856 The American Naturalist. [October, 
opment of the eyes in detecting danger—Necessity of leisure— 
Labours of parent-birds—Laborious and stealthy birds habitually 
poor in song—Flight in song: for parposes of display—Fluttering 
of wings a means of address—V entriloquism—Singing in chorus.” 
The study of bird-song, on the lines indicated by Mr. Rhoads and 
myself, is so new and so delightful a pursuit that I hasten to ask read- 
ers of THE AMERICAN NATURALIST to peruse his paper once more; for 
it is in America, so richly blessed with birds, that such investigations 
can be most easily developed, and that they promise the most accur- 
ate and helpful results.—CĦARLES A. WITcHELL. 
A Note on Dr. Herbert Nichols’ Paper (Amer. Nat., Sept., 
. Herbert Nichols’ paper on my article entitled 
“ A New Factor in Evolution” will understand that its intemperate 
spirit should rule out all reply. I may say, however, that Dr. Nich- 
ol’s “home thrusts” are all directed at my view of pleasure and pain, 
which he considers, quite mistakenly, the point of my paper. On the 
contrary the “factor” is entirely the influence of the individual’s adap- 
tations on the course of evolution; not at all the particular way in 
which the individual makes its adaptations. I took ve = reiterate 
this distinction in the paper, saying (Amer. Nar., 1896, p. 542-3) “So 
far we have been dealing exclusively with facts . . . . . without 
prejudicing the statement of fact at all, we may inquire into the 
actual working of the organism in making its adaptations. 
Before taking this up, I must repeat with emphasis that the piii 
taken in the foregoing pages, which simply makes the fact of ontogen- 
etic adaptation a factor in (race) development, is not involved in the 
solution of the farther question as to how the adaptations are secured.” 
So I see absolutely no point in Dr. Nichols’ criticisms. 
The other question, which involves pleasure and pain, is discussed in 
the latter part of my paper; but it is not that, but my book which 
Dr. Nichols attacks with the grossest misunderstanding. I do not 
at all believe the main things which he attributes to me; first, the 
position that there are no pain nerves, and second, that there is a 
“ psychic factor” which is an “efficient cause” in evolution. Psycholo- 
gists know Dr. Nichols’ hobby and allow for his intemperateness. 
. MARK BALDWIN. 
Princeton, Sept. 25, 1896. 
