Scoperta dei report (1962) Rapporti ricerche discoveryreports31inst Anno: 1962 402 report di rilevamento carta (leggi, 1959) ed è stato mostrato che i campioni prelevati nell'Antartico nel periodo di 5 mesi da ottobre a febbraio può essere considerato rappresentativo dell'andamento della crescita fetale, ma che la migrazione differenziale al di fuori della zona incide sulla validità dei campioni a partire da marzo. Una simile migrazione differenziale nella zona dei mezzi a molla che molto gli embrioni precoci (meno di un mese dopo il concepimento) tenderà ad essere assente in campioni antartico. Per effetto di questo woul
1711 x 1169 px | 29 x 19,8 cm | 11,4 x 7,8 inches | 150dpi
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Discovery reports (1962) Discovery reports discoveryreports31inst Year: 1962 402 DISCOVERY REPORTS paper (Laws, 1959 a) and it was shown that the samples taken in the Antarctic in the period of 5 months from October to February may be considered to be representative of the progress of foetal growth, but that differential migration out of the area affects the validity of the samples from March onwards. A similar differential migration into the area in spring means that very early embryos (less than one month post-conception) will tend to be absent in antarctic samples. The effect of this would be most marked in the earlier months, prior to November, for which in any case very few length records are available. It is estimated that, in addition to the 956 foetuses recorded in Table io, little more than 50 (some 5) would have to be added to the lower size groups of the frequency distributions for October and J JASONDJ FMA MONTHS Text-fig. 30. Mean curve of foetal growth and monthly foetal length frequencies of southern hemisphere fin whales; class interval 0-2 m. November, and the higher size groups of the March and April samples, to overcome this bias. The effect of this small error on the frequency distribution of pairing, which is now to be calculated, means that the pairing frequencies for the early months of the breeding season and for the late months will be slightly under-rep resented. This is thought to have a negligible effect on the shape of the pairing curve. The effect of individual variation in growth-rates must also be considered. Zemskiy (19500) states that male and female foetuses grow at different rates. Kimura (1957, p. 113) studied the difference in length between twins of different sexes, but found that in 57 of cases there was no difference, and the remainder were almost equally divided between pairs in which the female was larger and pairs in which the male was larger. No distinction as to sex need, therefore, be made in studying foetal growt
