302 DISCOVERY REPORTS 



(0-64 tons). A regression line has also been drawn for the small series of humpback whale records which 

 suggests a mean birth weight (at a length of 4-56 m.) of about 1300 kg (1-28 tons). 



Almost all of this growth takes place in the last part of pregnancy. Mackintosh and Wheeler (1929, 

 p. 426) pointed out that a 0-5 m. foetus 'differs very little in appearance and bodily proportions from 

 the adult and so far as the internal structures are concerned the organs are probably all laid down by 

 the time the foetus has reached o-i m. It is therefore natural to suppose that the actual linear rate 



Table 6. Length and weight data for 115 baleen whale foetuses 



Fin whale foetuses 



of growth is extremely slow while the foetus grows from zero to about o-i m. compared with its 

 subsequent growth up to the end of gestation, for from between o-i and 0-5 m. up to birth at 6-7 m. 

 development consists mainly in increase in size. ' Comparison of PI. XIII, figs, i and 2, illustrates this 

 point. The 18-5 cm. foetus shown in fig. i is already typically cetacean in appearance (2 months 

 after conception) and even at this age does not differ very markedly in bodily proportions from the 

 7-46 m. foetus illustrated in fig. 2. 



