For the mechanism of the frog's respiration, see Gaupp, Arch. Anat. 1896, p. 239.

[24]

Boulenger, The Tailless Batrachians of Europe, Ray Soc. 1896.

[25]

Zeitschr. wiss. Zool. xlix. 1889, p. 583.

[26]

Amer. Natural, xxv. 1891, p. 753.

[27]

Zool. Jahrb. Syst. vi. 1892, p. 447.

[28]