98
widening and becoming deeper, flowing quietly and gently, like the more mature thought of manhood. The very scum in some parts teems with animal life, skimming the surface of the water—
"——— Flumina libant
Summa leves."—Virgil.
and we carefully place portions of it in our bottles,—and in your leisure, beauties such as few of you have ever imagined, may be discovered therein; hair-like filaments of the most exquisite patterns conceivable,—long tubular cells containing beautiful green spiral coils, or numerous spherical granules or zoospores, moving restlessly about, and frequently striking against the walls of the cell, as if anxious to escape from confinement. This point gained after a while, they speedily begin to move hither and thither, now wheeling round and round, now oscillating from side to side, and now as if from sheer fatigue remaining quiescent. "Truly wonderful," says Hassell, in his "Freshwater Algæ," "is the velocity with which these microscopic objects progress, their relative speed far surpassing that of the fleetest race-horse. After a time, however, which frequently extends to some two or three hours, the motion becomes much retarded, and at length after faint struggles, entirely ceases, and the Zoospores then lie as though dead;—not so, nevertheless—they have merely lost the power of locomotion,—the vital principle is still active within them, and they are seen to expand, to become partitioned, and if the species be of an attached kind, each Zoospore will emit from its transparent extremity two or more radicles, whereby it becomes finally and
