|THE FROG AS PARENT.|
JOHNS HOPKINS UNIVERSITY.
IN the life of a common frog or toad we seem to find none that altruistic solicitude for the welfare of the helpless younger members of society, that we so fondly attribute as guide in many of our own actions. In clamorous spring reunions these cold-blooded creatures deposit their eggs in the water and go their way in search of food—not knowing whether some or many of the eggs will run a normal course through tadpole or pollywog states to tailless adults, or fall a prey to hungry ducks, or more insatiable naturalists in search of 'material' for study.
The naturalists' belief that these Amphibia are closely akin to fish in many ways is borne out in their breeding habits; for, like fish, they have more or less complex 'instincts' that lead the males and females together at the laying season, and then, like fish, they separate till the next period of egg-laying. The eggs, discharged in the water, are fertilized outside the body, and undergo a process of cleavage or cell-multiplication, thus gradually differentiating into active larvæ or tadpole? without any care from the parents. The tadpole leads its own independent fishlike life for months or years, till—if not destroyed—the critical period of transformation arrives. This passed, the young frog or toad has only its instincts to guide it in learning the new life and nothing to learn from its parents—unless perchance they may be near enough to endeavor to swallow it alive.
Yet even here we might fancy some thought for the morrow of the species—the eggs are generally laid in the right place—according to the kind of frog or toad—to have enough water and not too many enemies for the young, while the protecting jelly mass about the eggs is often rather carefully fastened to plants or sticks, thus keeping them near the surface of the water and in optimum conditions for hatching.
But this is not clear until we see some of the extremes to which such prevision for the next generation is carried in certain members of this group. Just as amongst fish there are a few with most remarkable habits—the male stickleback watching and protecting the eggs in his carefully made nest—so, if we look far enough, we find frogs and toads that show most exemplary solicitude for the young. In Europe, Asia, Africa and in South America such curious life-histories are more or less common.