This could be seen in the
warm months, but now, not a snail of the countless millions can be seen.
They have gone down in search of "hard-pan," there to hibernate until
next April. The land snail (_Helix pomatia_) sleeps four months during
the year, and does not throw off the calcareous lid that protects it
during this time until the day temperature has reached 12 deg. Cent. Prairie
dogs feel the effect of temperature as low as this.
In Cuba reptiles hibernate between 7 deg. and 24 deg. Cent., according to the
species. In warmer countries, snakes, lizards, frogs, etc., fall into a
state called chill coma that precisely resembles winter sleep, but their
temperature is far above that at which hibernating animals of the north
are still active. The state of hibernation is not the direct result of
an extreme of heat or cold, but rather is caused by a departure from the
optimum. In the snail its normal temperature is about the same as the
water, and being a poor heat producer it is not surprising that when
the water grows colder the animal is forced to succumb; but it is
a remarkable fact that warm-blooded animals like many of the
above-mentioned, whose bodies are maintained by internal processes at a
high temperature of 26 deg.
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