blood, changes its mode of growth; it never forms blood-vessels at all, but divides into free red (hæmoglobinous) cells or red blood corpuscles, which float in the lymph of the cœlom. There is no blood-vascular system produced in these worms, but the "cells" of the tissue which would in other worms form blood-vessels break up into red corpuscles, which, mixing with the lymph, bring it into the condition of "hæmolymph," identical with the blood of Vertebrates! In the molluscs, snails, whelks, oysters, clams, and cuttle-fishes there is a further, variation. The same two fluids and two systems of spaces are present as in the earth-worm, but the cœlomic space and fluid have been nearly blocked up and obliterated by the swelling-up and great size of the proper hæmal vessels. Only in rare cases is the blood of molluscs coloured red by hæmoglobin, usually it is of a pale blue colour. There is still left a pericardial cœlom, a space around the heart, and from this some fine lymph-holding vessels ramify amongst the tissues, but the chief spaces in the body are dilated parts of the true hæmal system. In Insects and Crustacea (say cockroach and lobster) this process is carried still further. The great cœlom, so well developed in the Chætopod worms, and the Sea-urchins and Star-fishes, and retaining quite a large development also in the Vertebrates, is nowhere to be found. The swollen blood-vessels have squeezed it out of existence, except for certain sack-like remnants which enclose separately the ovaries, and the testes, and the kidneys, and have each its opening to the exterior conveying the products of those important organs to the outer world. Thus we gain a brief insight into the true history of the lymphatic system and its vicissitudes in the lower animals and in man. CHAPTER XXXIV THE BLOOD AND ITS CIRCULATION RED, crimson, scarlet, hot, the river of life, the carrier of all that is good and all that is bad by its myriad streams through our bodies; the rarest, most precious, most gorgeous of fluids; the daughter of the salt ocean, finer and more worshipful even than the waters of the great mother, the sea; the badge of horror and of accursed cruelty, yet also the emblem of nobility, of generosity, of all that is near and dear, of all that is splendid and beautiful; the blush of modesty and the flag of rage; the giver of coral lips and glowing cheeks to youth and health, and no less of the ruddy nose which women hide with powder and men bravely bear without concealment! Such is the blood, and it is no wonder that the mere sight of it has always had an overpowering fascination for mankind.