The problem of aging whales is an important one, and one to which much thought has been given. Actually, it is desirable to know at what age sexual maturity occurs; at what age physical maturity; at what age reproduction is no longer possible, and lastly, the age at death. In addition, we need to know the gestation period and the average number of pregnancies of which the female is capable. Many of these statistics can be obtained from the examination of a freshly killed whale. Such age determinations are made on every specimen which comes aboard the factory ships and also at the shore stations. There is some doubt as to the accuracy of some of these. Physical maturity is delayed in whales for many years, and it is judged complete when the cartilaginous end plates fuse to each vertebrum (backbone). After fusion, further lineal growth is impossible and after this time whales have been noted to shrink slightly each year. The other structures which a biologist collects for aging are the ovaries of the female whale. These are sliced across into half-inch slabs, and the number of exposed grayish masses are counted. There is one of these structures produced for each pregnancy, and they persist as scar tissue throughout the life of the whale. These structures are functional during pregnancy and nursing and are responsible for a successful pregnancy. A count of these gives the investigator the total number of offspring which have been produced. If one assumes that the whale has not missed an opportunity to produce a baby, the count of these gives the age, assuming one knows the age of sexual maturity and the maximum length of bearing. In recent years other structures have been tried for aging, so that males might also be aged, as well as females past the reproductive period. The best structure is the cylinder of wax which fills the outer canal of the ear leading to the eardrum. This enlarges as the whale grows, and the growth is marked by banding very similar in appearance to tree rings. Slicing the plug, the rings can be exposed and counted. There are produced but two rings a year. Toothed whales can be aged by sawing the teeth in half and noting the banding. Baleen also is periodically enlarged, but this is more difficult to check. _Distribution and Population Rise_