Strangely enough a clew to their wanderings has been given by a parasite which lives upon the whale’s body. This Copepod, known as _Penella antarctica_, produces a peculiar white or grayish oval scar two or three inches in length, which for many years was supposed to be a feature of the sei whale’s coloration. I suspected at first sight that these spots were scars left by a parasite of some sort, but it was not until two years later that my suspicion was proved correct and the animal itself discovered. It was doubly interesting to find that this parasite is an Antarctic species which has never been known from the North Atlantic or Pacific Ocean. On the second French Antarctic Expedition Dr. Liouville discovered that all the sei whales taken in the South Atlantic were bristling with these parasites but except in rare cases the whales of the north have none of them _in situ_. The parasites are short-lived and probably die or break off during the northward travels of their hosts, leaving only the scars behind. It is not probable that _all_ sei whales make this migration annually—in fact it is highly improbable that such is the case—but herds are apparently formed which visit certain localities every year, now and then being reinforced by individuals which have come either from the Antarctic into the north or vice versa. [Illustration: A blue whale, eighty-five feet long, at Kyuquot, Vancouver Island. This is the largest animal that has lived upon the earth or in its waters, so far as is known at the present time. ] The migration of the large Cetacea is a subject about which very little is known and of which but few positive statements can be made. In the case of only one species, the California gray whale, can we tell exactly where, when, and how far the animals travel, for this coast-loving whale migrates as regularly as do birds and the paths of its wanderings are known. [Illustration: “In the water the sei whale may be easily recognized at a considerable distance by the form of the spout and the high dorsal fin which is prominently displayed as the animal swims at the surface.” ] In the water the sei whale may be easily recognized at a considerable distance by the form of the spout and the high dorsal fin which is prominently displayed as the animal swims at the surface. This species does not dive very deeply and when feeding its movements can usually be traced by the disturbed water, as well as by the clouds of birds hovering about the tiny sea animals which come to the surface. [Illustration: “The sei whale has a roving disposition and wanders restlessly from one coast to another, sometimes ... suddenly appearing in waters where it has never before been known.” ]