214 Animal Music, its Nature and Origin. [ April, 
ciscus whilst singing a cadence of three notes, in true musical 
intervals and with a clear musical tone.” 
The Rev. S. Lockwood writes in the AMERICAN NATURALIST 
(v1) of a most interesting singing mouse, Hesperomys cognatus, 
and fortunately gives the music, written by his son (Song No. 39). 
He says, “ Although she had no ear for time, yet she would keep 
to the key of B (two flats) and strictly in a major key. Her soft 
clear voice falls an octave with all the precision possible, then at, 
the wind up it rises again into a very quick trill on C sharp and 
D. When singing whilst turning in her wheel, and suddenly 
thrown on her back by its stoppage, as if in surprise, she would 
roll off four or five notes in a higher octave, and in a greatly 
increased loudness of voice.’ 
In answer to some inquiries, Mr. Lockwood kindly writes me 
as follows: “ Octaves, fifths and thirds were usually selected for 
the long intervals of Hesperomys’ song. I have had and still 
have singing guinea pigs, Cavia cobaia. What is said of my 
Hesperomys is in the main true of the Cavia. There are other 
rodents that sing, Mus musculus, or house mouse; the rat, Mus 
rattus; the white-footed mouse, Hesperomys leuripits ; the wood- 
chuck, Arctomys monax, and the squirrels.” Recent numbers of 
Nature (vi) and the Popular Science Monthly (vu) contain brief 
accounts of singing mice. That in the former confirms some 
curious phenomena observed by Mr. Lockwood—the singing of 
an air with an accompaniment, and the influence of fright as well 
as joy in starting the song. 
It is doubtful whether true music is produced by any inverte- 
brates. There seems to be no provision in the ear for the exact 
discrimination of pitch, and the sounds are instrumental rather 
than vocal, being generally produced by stridulation. Some refer- 
ences, however, are given with the others to what has been writ- 
ten on this subject (xxir to xxv1, see also 11, pp. 274, 289, 301). 
For assistance in my work of collecting and studying animal 
songs I am much indebted, especially to Mr. Wilson F lagg, Prof. 
E. R. Sill, Dr. Elliott Coues, Rev. S. Lockwood, Mr. H. A. Pur- 
die, Mr. Robert Ridgway, Miss Alice Bacon, Mr. H. D. Minot and 
Dr. P L. Hatch. It was necessary that the work should be 
largely one of compilation, for the material had never been 
brought together before. «Thus the attempt has much of a 
pioneer character, and my chief hope is to direct attention to this 
_ important field of study, where acute observation is very much 
