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DISCOVERY REPORTS 



detection or elimination of any possible sub-specific or racial distinctions such as might 

 be associated with distribution or migrations. 



2. An investigation of the reproductive processes, breeding habits and growth. 



3. The examination of the interrelations of breeding, nourishment, distribution and 

 local fluctuations of the whales. 



The results of this work may be summarized as follows : 



By a series of measurements carried out on a large number of whales, the normal 

 bodily proportions of southern Blue and Fin whales, and the extent to which they vary, 

 have been defined ; and the same has been done for various external features by means 

 of detailed descriptions of the colour, baleen, ventral grooves and hair. 



It has been shown in both species that no distinction can be drawn between the 

 whales of South Georgia and South West Africa, and that there are no indications 

 that more than one race exists together in either locality. 



The series of measurements, as well as the notes on external characters, provides a 

 standard from which it will be easy to ascertain if Blue and Fin whales examined in the 

 northern hemisphere or from any other part of the world fall within the limits of 

 variation observed in South Georgia and on the south-west coast of Africa. 



Attention is drawn to certain marked changes which take place in the bodily pro- 

 portions as the whale grows, and which, at one point, may be associated with the attain- 

 ment of physical maturity. 



Leading up to the problems of breeding and growth, an account is given of the 

 reproductive organs, of which the most important are the ovaries. It is a peculiarity 

 of the ovaries of these whales that the corpus luteum formed at each ovulation persists 

 in a recognizable form for a very long time, probably for years, with the result that 

 accumulations of old corpora lutea give some indication as to the number of ovulations 

 which may have taken place. Other conclusions to be drawn from the reproductive 

 organs relate to the determination of sexual maturity and the progress of the sexual cycle 

 throughout the year. It may be regarded as reasonably certain that Blue and Fin whales 

 are polyoestrous. 



From an estimation of the ratios of immature whales in the catches the important 

 fact emerges that a very high proportion of immature whales is killed. Sexual maturity 

 is reached on the average at the following lengths : 



Male Blue whales 

 Female Blue whales 



22-6 m. 

 237 m. 



Male Fin whales 

 Female Fin whales 



19-4 m. 

 20-0 m. 



By application of these figures to the whales examined during the work the per- 

 centages of immature whales are found to be as follows : 



