Page:Popular Science Monthly Volume 31.djvu/856

836 feel sure it is a neat and appropriate epithet.) Where the chances of infant mortality rule high, the mother-animal must produce vast numbers of small and ill-supplied eggs in order to provide against the adverse possibilities. That careless parent, the cod, who lays her spawn unprotected upon the shallow banks, for thousands of greedy enemies to devour, often produces at a single birth as many as from four to nine million separate eggs. But just in proportion as the eggs and young are more efficiently guarded and provided for in life does it become possible to economize in the number of germs originally produced, and to give each at the outset a fair supply of yolk to start well in life with. Compare the myriad tiny black seeds of the poppy, which take their even chances anywhere that fate may carry them, with the richly stored bean or pea or filbert, well provided with nutriment for the growing seedling, and you will see at once the force of the analogy here intended. The codfish lays a great many ill-supplied eggs, and lets them shift for themselves in the open sea as best they may, on the off chance of one among four million or so reaching maturity; the stickleback lays comparatively few large and well-supplied eggs, but the amiable father watches with tender solicitude over the safety of all, so that on an average two at least out of each mother's small brood must needs survive to years of adult sticklebackhood.

I have spoken of the stickleback genus so far as though, like the French Republic, it were one and indivisible. Such, however, is not the case. The family has split up into several minor sections, each adapted to particular situations. There are some ten known species of stickleback, and the facts hitherto noted apply most especially (save in a few instances) to one above all others among them, the common British three-spined stickleback. All the varieties are pretty much alike in all essential points, having the same long, flat-sided bodies, with hard cheeks, while parts of the skeleton usually form an external coat of mail, and grow out into large scutes or shields along the sides. On their back are more or fewer of the spines from which the entire group take their generic name, nine in one species, fifteen in another, three only in the commonest English form, and no more than two in the pretty little North American example. One of them has adapted itself to brackish water and the open sea; the others are all fresh-water forms, though most of them at a pinch can manage a sea-voyage without serious damage to their constitutions. They are a north temperate family by origin; in other words, they have sprung up in the rivers of the sub-Arctic zone, and have not yet spread beyond the Arctic and temperate regions of the northern hemisphere on both sides of the Atlantic.

Our common little British river stickleback, the familiar tittlebat of the Serpentine and the Hampstead Ponds, is the three-spined form (Gastrosteus aculeatus); and he has generally, in addition to his offensive spines, a series of defensive shields or plates along the gleaming