256 DISCOVERY REPORTS 



similarity of frequencies. In spite of the fact that the proportions of ovaries from 

 the different regions are not the same for the two years, it will be seen that the curves 

 are substantially of the same shape. 



homogeneity of adult catch. The close similarity of the two frequency curves can 

 hardly be a coincidence. In the season 1934-5 tne majority of the ovaries were taken in 

 the Kerguelen Area, whereas in 1935-6 those from the Bouvet Area predominated. There 

 are points of similarity between these two groups of material. The smaller collections 

 from the other areas are probably too small to show any definite features, but added to 

 the main collection they contribute to the great similarity of the total samples of ovaries 

 for the two seasons. The fact that smoothing of the aggregate corpora lutea frequency 

 curves is necessary in order to bring out their similarity of contour and gradient is in 

 itself evidence that the collections of ovaries could with advantage have been two or three 

 times as large. In view of the practical difficulties of obtaining and examining such a 

 large collection we must be content with the numbers available, which after legitimate 

 manipulation show striking similarity in the two seasons. The results suggest that the 

 age composition of the Antarctic Blue female population from which the catch is drawn 

 is similar in all the widely different regions from which this material was taken. It 

 would then appear that one area does not harbour a particular age of whales and the 

 adult population is approximately homogeneous in character and is freely distributed 

 over the whole of the Antarctic whaling grounds from about 58 S to the edge of the pack 

 and about 30 W to ioo° E, these being the geographical limits of these collections. 



This conclusion, tentative as it must be, may or may not be confirmed by the results 

 from a further collection of ovaries now being made (season of 1936-7). In any case it 

 may be held to apply only to the adult portion of the population, and the possibility that 

 immature whales follow definite migratory routes from the tropics to the Antarctic and 

 tend to be concentrated in certain regions of the latter is by no means ruled out. It is 

 hoped that information on this point will be gleaned from an examination of length 

 frequencies of whales taken in pelagic whaling in the near future. 



It will be seen that there are certain fairly conspicuous peaks and abysses in the two 

 curves in Fig. 9, which since they withstand smoothing are probably of some signi- 

 ficance. In Fig. 10 the two curves are shown together, and it is interesting to note that 

 with one or two minor exceptions there seems to be some relation between the peaks and 

 depressions. The points thought to be related are marked A, A';B, B', etc. 



Evidence has been adduced above (pp. 246-50) that an average of rather more than one 

 corpus luteum is added to the ovaries of the Antarctic adult stock in one year, and some 

 confirmation of this is to be found in Fig. n. If the two curves are taken to represent 

 the same stock of whales in two successive seasons the peak, for example at eight 

 corpora lutea in the 1934-5 curve (marked B in the figure), should reappear in the curve 

 f° r J 93 5-6 at between nine and ten corpora lutea, and it will be seen that in fact it 

 does so at B'. A and A' do not fit so well. The increment indicated by the relation of 

 A to A is two corpora lutea. The curves do not agree so well in contour over this part. 

 (Curiously enough an almost perfect agreement of contour and an increment from A to 



