. 01 2 3 4 5 6 7 8 9 10 II (2 13 14 15 '—'o—*«- *g-'o (f^onths) ? Text-fig. 12. Diagram showing estimated mean foetal growth curves of five Balaenopterids and three Odontocetes. For comparative purposes the origin of the curves is taken as i„. {Bm = Balaenoptera muscultis; Bp = 5. physalus; Bb = B. borealis; Ba = B. acutorostrata; Mn = Megaptera novaeangliae; Fc = Physeter catodon; D\ = Delphinapterus leucas; Pp = Phocaena phocoena). increased skewness, and the distributions for February and March show a reversal of this trend. The same inferences are drawn from the shapes of these monthly len
. 01 2 3 4 5 6 7 8 9 10 II (2 13 14 15 '—'o—*«- *g-'o (f^onths) ? Text-fig. 12. Diagram showing estimated mean foetal growth curves of five Balaenopterids and three Odontocetes. For comparative purposes the origin of the curves is taken as i„. {Bm = Balaenoptera muscultis; Bp = 5. physalus; Bb = B. borealis; Ba = B. acutorostrata; Mn = Megaptera novaeangliae; Fc = Physeter catodon; D\ = Delphinapterus leucas; Pp = Phocaena phocoena). increased skewness, and the distributions for February and March show a reversal of this trend. The same inferences are drawn from the shapes of these monthly length-frequency distributions as for the fin whale frequency distributions, and an exponential curve has been fitted to the mean foetal lengths for November, December, January and February. This curve attains the average neonatal length ( m.) in mid-April. The slope of the linear segment of the blue whale growth curve is based on very sparse data. It has been plotted with reference to six records for October, two for September, two for August and two for July. It cuts the abscissa at the end of June and the period from conception to Lt^ is estimated to be 30 days, slightly shorter than the similar period in the fin whale (33 days) because the slope of the linear segment of the growth curve is steeper (Table i). This gives an estimated mean date of conception in the fourth week in May, which fits quite well with inferences made from other evidence. The estimated gestation period of the blue whale is therefore lof months and although less confidence
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Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
