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Description of Chart. For further details see 
citations in text. 
Graph 1. A white-footed wood mouse (Pero- 
myscus leucopus noveboracensis Fischer) in an 
evaporation gradient due to differences in air ve- 
locity. The figures at the beginning of the graph 
indicate the evaporation for the experimental 
period in tenths cubic centimeters of water; those 
at the end indicate air velocity in meters per sec- 
ond. (After Chenoweth.) 
Graph 2. A white-footed wood mouse in an air 
humidity gradient. The figures at the beginning 
of the graph indicate evaporation and at the end 
relative humidity in per cent. of saturation. 
(After Chenoweth.) 
Graph 3. A horned lizard (Phrynosoma modestum 
Gir.) in air humidity gradient; figures as in 2. 
(After Weese.) 
Graph 4. A horned lizard in a substratum tem- 
perature gradient; the figures indicate tempera- 
ture in degrees centigrade. (From Weese, unpub- 
lished.) 
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Graph 5. A common toad (Bufo lentiginosus 
Shaw) in an air humidity gradient. Figures as in 
2 and 3. 
Graph 6. A small sunfish (Lepomis humilis 
Gir.) in an ammonia gradient in alkaline water. 
Maximum concentration of ammonia at left, 7-10 
pt. per million. 
Graph 7. A ground beetle (Platynus cupripen- 
nis Say) in a light intensity gradient. 
Graph 8. The same individual ground beetle in 
an oblique cage intensity-direction gradient. 
Graph 9. An earthworm (Helodrilus caliginosus) 
in an air moisture gradient. Figures as in 2, 3 
and 5. (From Heimburger, unpublished.) 
Graph 10. A single Paramecium in a tempera- 
ture gradient in which the cool end was near the 
optimum. 
Graph 11. A single Paramecium in a tempera- 
ture gradient which resulted in death at the end of 
12 minutes. 
