BALEEN WHALES 291 



curve is slightly less than the slope of the sperm whale curve (Text-fig. 12) and Lt^ is very close to 

 this value for the sperm whale in which L^q — 34 days. 



This suggests that it is correct to interpret the middle phase of foetal growth as linear in the 

 humpback whale at least and probably this also holds good for other baleen whales. The exponential 

 fit to the second part does not rest on a firm foundation and, as will be seen in the more detailed 



ASONDJ FM 

 <-^o-^ MONTHS 



Text-fig. 6. Foetal growth in length of southern hemisphere humpback whale, Megaptera novaeangliae. 



Points are mean values. See text for explanation. 



u 

 u 



5 



4 - 



3 - 



I 2 - 



z 



UJ 



MONTHS 



Text-fig. 7. Foetal growth in length of northern hemisphere sei whale, Balaenoptera borealis. 



Points represent monthly means. 



discussion of blue and fin whales, the variability in the monthly foetal lengths is such that foetal 

 growth could be described by a series of linear phases of different slope, or by a more complicated general 

 formula. The logarithmic plot has been accepted as the most simple fit for all the species considered. 

 As foetal growth of baleen whales cannot be described by a linear plot of foetal length throughout 

 gestation, the values of L^ cannot be derived by reference to the length of gestation. However, it is 



