. Fig. 60. Humpback whale. Average lengths of immature whales by months. (1927), who examined a few Humpbacks in California, suggested that these whales be- come sexually mature while they are yet quite young, a suggestion which is here shown to be correct. The age classes of Humpback whales cannot be deduced from the number of corpora lutea in the ovaries, as can those of the Blue, Fin and Sei whales, because of the shortness of the complete breeding cycle in this species and the indication already shown that pregnancy may sometimes occur twice every three years, or at least that an extra pre
. Fig. 60. Humpback whale. Average lengths of immature whales by months. (1927), who examined a few Humpbacks in California, suggested that these whales be- come sexually mature while they are yet quite young, a suggestion which is here shown to be correct. The age classes of Humpback whales cannot be deduced from the number of corpora lutea in the ovaries, as can those of the Blue, Fin and Sei whales, because of the shortness of the complete breeding cycle in this species and the indication already shown that pregnancy may sometimes occur twice every three years, or at least that an extra preg- nancy may be interpolated in a more usual two-year cycle. The most that can be said is that the whales with the lowest numbers of corpora lutea (one or two) are in their second year and aged from eighteen months to two years. The classes shown by numbers of corpora lutea after this age may be separated by one and a half years in some cases and two years in others, so that taking into account also the paucity of the data, no indication can be given of the ages of the older whales by this means (cf. Wheeler, 1930).
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