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specimens listed below, which I have examined, Smith and Taylor (1948: 99) give a number of localities for this species. Most of these have been plotted in Figure 3. Distrito Federal: Mexico (AMNH 1289); vicinity of Guadalupe (AMNH 12216-27, 13366-78). Guanajuato: Guanajuato (USMN 9891, 12684, 26155); Santa Rosa (USMN 47206). Jalisco: Teocaltiche (UIMNH 32308). Mexico: Lagunilla de Ojuelos, 5 mi. W Toluca (AMNH 55265-66). Michoacan: Tupitaro (USMN 10239 [3 specimens], 10243 [3 specimens], 10251, 1025355, 10258); Sahuayo (USMN 113735); 5 mi. NW Maravatio (UIMNH 32304-05). Puebla: Chignahuapan (USMN 21454-59). San Luis Potosi: Arriaga (LSUMZ 2520-38, 2554-55); Bledos (LSUMZ 2549-50, 4275-77, 4285); 21 km. W Illesca (LSUMZ 2317); Laguna de las Rusias (LSUMZ 5654); Presa Gonzales Santos, 10 mi. SW San Luis Potosi (LSUMZ 4303-06); Presa Prudentia (LSUMZ 5668); Presa San Jose, 4 mi. SW San Luis Potosi (LSUMZ 4307-10); Sierra San Miguel, 7500 ft. (LSUMZ 4973).

AMONG the many bright green tree frogs in South America the green coloration may be brought about by two entirely different sets of physiological factors. In one type the skin contains three types of chromatophores arranged in different layers. The most superficial layer is made up of lipophores that are filled with a yellow, fatty material. Deep to the lipophores is a layer of guanophores packed with crystals of guanine, a chemical allied to uric acid. The deepest layer is that of the melanophores. When visible light falls on the skin the light of shorter wave lengths (greens, blues, lavenders) is reflected back by the guanophores while the longer wave lengths (reds, oranges, yellows) are absorbed by the melanophores. As the shorter light rays are reflected by the guanophores back through the lipophores the blues and lavenders tend to be absorbed while the greens are transmitted so that the skin appears green to the human eye. If, however, the lipophores are altered or destroyed by preserving fluid the blues and lavenders are transmitted so that the preserved frog appears blue or some shade of lavender to the human eye. Examples of skin pigmentation of this type are found in Phyllomedusa bicolor (blue in preservative), Phyllomedusa hypochondrialis, and Centrolenella geijskesi (lavender in preservative). In addition to green frogs of this type there are others in which the green coloration is due to an accumulation of a chemical (biliverdin) in the skin rather than to chromatophores. In this latter group the chemical may be altered or destroyed by the preserving fluid so that the specimen fades to a milky white. As examples of this type we can mention Hyla punctata, Hyla granosa, and Sphoenorhynchus aurantiacus. It is one of the latter type that we describe here.

Data are presented on the amount of DNA in absorption units per nucleus for 43 species of frogs belonging to nine families. Values range from 4.5 au/nucleus in Scaphiopus holbrookii to 26 in Rana catesbeiana. Comparison of amounts of nuclear DNA and of minimum known durations of the larval stages indicates that the species that have the least amounts of nuclear DNA pass through the larval stages most rapidly. Data are also presented on the amount of nuclear DNA of two species of salamanders. It is suggested that a high level of DNA and low rate of development restrict some frogs and salamanders to the vicinity of permanent water while a low level of DNA and rapid rate of development allow other frogs to invade arid environments.