Chap. XII. 
AMPHIBIANS. 
27 
These animals, however, offer one interesting sexual 
difference, namely in the musical powers possessed by 
the males ; but to speak of music, when applied to the 
discordant and overwhelming sounds emitted by male 
bull-frogs and some other species, seems, according to 
our taste, a singularly inappropriate expression. Never- 
theless certain frogs sing in a decidedly pleasing man- 
ner. Near Eio de Janeiro I used often to sit in the 
evening to listen to a number of little Hylae, which, 
Fig. 32. Megalophrys montana. The two left-hand figures, the male ; the two 
right-hand figures, the female. 
perched on blades of grass close to the water, sent 
forth sweet chirping notes in harmony. The various 
sounds are emitted chiefly by the males during the 
breeding-season, as in the case of the croaking of our 
common frog.^^ In accordance with this fact the vocal 
organs of the males are more highly developed than 
those of the females. In some genera the males alone 
"^2 Bell, ‘ History of British Kep tiles,’ 1819, p. 93: 
