or calf at a birth, and seldom produce more than a couple. Moreover,
in all these higher cases alike, the young are fed with milk by the
mother, and so spared the trouble of providing for themselves in their
early days, like the young codfish or the baby tadpole. Starvation at
the outset is reduced to a minimum.

It is interesting to note, too, that anticipations of higher types, so
to speak, often occur among lower races. An animal here and there
among the simpler forms hits upon some device essentially similar to
that of some higher group with which it is really quite unrelated. For
example, those who have read my account of the common earwig (given in
the sixth chapter of "Flashlights on Nature") will recollect how that
lowly insect sits on her eggs much as a hen does, and brings up her
brood of callow grubs as if they were chickens. In much the same way,
anticipations of the mammalian type occur pretty frequently among
lower animals. Our commonest English lizard, for example, which
frequents moors and sandhills, does not lay or deposit its eggs at
all, but hatches them out in its own body, and so apparently brings
them forth alive: while among snakes, the same habit occurs in the
adder or viper. The very name _viper_, indeed, is a corruption of
_vivipara_, the snake which produces living young. Still more closely
do some birds resemble mammals in the habit of secreting a sort of
milk for the sustenance of their nestlings. Most people think the
phrase "pigeon's milk" is much like the phrase "the horse-marines," a
burlesque name for an absurd and impossible monstrosity. But it is
nothing of the sort: it answers to a real fact in the economy of
certain doves, which eat grain or seeds, grind and digest it in their
own gizzards into a fine soft pulp or porridge, and then feed their
young with it from their crops and beaks. This is thus a sort of
bird-like imitation of milk. Only the cow or the goat takes grass or