Frogs and other amphibians stand higher in the scale of life than fish; they have acquired legs in place of fins, and lungs instead of gills; they can hop about on shore with perfect freedom.  Now, frogs still produce a great deal of spawn, as every one knows:  but the eggs in each brood are numbered in their case by hundreds, or at most by a thousand or two, not by millions as with many fishes.  The spawn hatches out as a rule in ponds, and we have all seen the little black tadpoles crowding the edges of the water in such innumerable masses that one would suppose the frogs to be developed from them must cover the length and breadth of England.  Yet what becomes of them all?  Hundreds are destroyed in the early tadpole stage—­eaten up or starved, or crowded out for want of air and space and water:  a few alone survive or develop four legs, and absorb their tails and hop on shore as tiny froglings.  Even then the massacre of the innocents continues.  Only a tithe of those which succeeded in quitting their native pond ever return to it full grown, to spawn in due time, and become the parents of further generations.

Lizards and other reptiles make an obvious advance on the frog type; they lay relatively few eggs, but they begin to care for their young.  The family is not here abandoned at birth, as among frogs, but is frequently tended and fed and overlooked by the mother.  In birds we have a still higher development of the same marked parental tendency; only three or four eggs are laid each year, as a rule, and on these eggs the mother sits, while both parents feed the callow nestlings till such time as they are able to take care of themselves and pick up their own living.  Among mammals, which stand undoubtedly at the head of created nature, the lower types, like mice and rabbits, have frequent broods of many young at a time; but the more advanced groups, such as the horses, cows, deer, and elephants, have usually one foal 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