THE STOCK OF WHALES 455 



In order to make a quantitative analysis of the constitution and variations of the 

 catches it is necessary to separate the whales of both species into what we may call 

 different "classes". These are as follows: 



" Pregnant or recently ovulated " refers to whales in which a functional corpus luteum 

 but no foetus was found. Such whales may be classed together since if a foetus was 

 missed it would probably be so small that for our purpose the whale could practically 

 be regarded as having "recently ovulated". 



There is little object in separating males into more than the sexually mature and 

 immature classes, but in the case of females some discrimination must be made between 

 whales in the various stages in the sexual cycle. 



The tables which follow show the ratios of the numbers of whales of each class which 

 were caught in successive months, in successive seasons at South Georgia, in the season 

 at South Africa, and in the whole period during which the observations were carried out. 



In a number of whales it was of course impossible to examine the reproductive 

 organs, generally on account of the decomposed condition of the carcass, and in 

 some it was possible to examine, for instance, the mammary glands but not the 

 internal genitalia. For this reason the exact number of whales in each class cannot be 

 stated, but in order to give as accurate a comparison as possible between the numbers 

 in each class, the number of whales, for example pregnant or lactating, are expressed 

 as percentages of the number of whales in which the uterus or mammary glands re- 

 spectively were examined. This applies only to the sub-classes of adult females. 



Columns 8, 9 and 10 show the numbers of whales in which either some or all of 

 the genitalia were examined. Thus in column 12, in January 1927 (1926-7 season), we 

 see that 47 per cent of the thirty-two whales, quoted in column 8 as having had their 

 uteri examined during that month, were pregnant. 



Percentages are calculated to the nearest unit. 



Reference should first be made to the total class ratios of all the Blue whales and all 

 the Fin whales. In these figures we find a restatement of some of the results which 

 have already been put forward. A relatively large number of immature whales, for 

 instance, are caught, amounting in the case of Blue males and females to 55 per cent 

 and 54 per cent respectively and Fin whales to 38 per cent and 41 per cent respectively. 

 Even when the South African whales are left out of account, the figures for South 

 Georgia show a high proportion of immature whales, at least in the case of Blue whales. 

 About 3 1 per cent of the adult Blue whales and 46 per cent of the adult Fin whales 

 are pregnant, and, as already explained, it may be argued from this that in all 



