Reliable data upon the breeding habits of all large whales are obviously difficult to secure and, except in the case of the California gray whale, it is impossible to state with certainty many facts upon this subject. Probably the period of gestation in the humpback is about one year and the calves are from fourteen to sixteen feet long when born. On June 16, 1908, at Sechart, a young humpback was killed with its mother. The calf had nothing but milk in its stomach and milk was flowing from both teats of the parent. I estimated that this baby humpback was about three months old and since birth had probably almost doubled its length. [Illustration: A humpback partly in the water at the station in North Japan. The whale is lying on its side with the breast and flipper showing. ] Although all the fin whales probably mate chiefly in the early spring, nevertheless pairing is deferred until later in the year among some individuals, as fœtal specimens show. Pregnant females always have very thick, fat blubber and yield a large amount of oil. Except in very rare cases all the large whales have but one young at a birth and although several instances of humpback twins have been recorded it is certainly very unusual. How long the calf lives upon milk is problematical, but it can hardly be more than six months. The rate of growth of large whales is so exceedingly rapid that the calf would undoubtedly be able to care for itself very soon after birth. The two teats of all cetaceans are concealed in slits on either side of the genital opening. In a humpback whale each teat is the thickness of a man’s thumb and two inches long. In the female humpback taken at Sechart with the nursing calf, the milk glands under the blubber had become greatly enlarged and were like an elongated oval in shape; they were 4 feet 6 inches long, 42 inches wide at the lower, and 9 inches at the upper, end. By suddenly pressing the surrounding muscles the milk could be ejected 2 or 3 feet in a fair sized stream and it is in this way that the calf probably receives it. The young whale’s mouth is so constructed that it is impossible for the animal to suck, in the ordinary sense of the word, and the teat is much too short, even when protruded two or three inches, to be held between the thick, rounded lips. When the milk is ejected into the calf’s mouth apparently considerable sea water must go with it unless the mother lifts that portion of her body out of the water while the baby is nursing, which is probably the case.