3 68 DISCOVERY REPORTS 



tions being probably controlled by hydrographical and meteorological conditions. There 

 is nothing here inimical to the idea of a closed stock of whales, i.e. a body of whales 

 breeding in a certain area, migrating on a certain line and ending their food migration 

 in South Georgian waters or passing through these waters on their way farther south. 

 This idea indeed underlies the work on variation of seasonal concentrations just as it 

 is implied in the following remark from Kemp and Bennett (1932, p. 179): "The 

 considerable extension of the grounds during the recent four-year period, and the 

 fact that with the same number of whale-catchers fewer whales have been taken, 

 lends support to the generally held opinion that whales are now less abundant than 

 formerly". 



Drawing conclusions from the diminution in number of sexually mature individuals 

 taken off South Georgia and the South Shetlands, Harmer (193 1 , p. 100) says : " Another 

 conclusion which it seems legitimate to draw from these figures is that the whales do not 

 wander at random throughout the Antarctic area, but are to some extent separated into 

 assemblages which have preference for particular localities. If this were not the case, 

 it would be difficult to account for the fact that the percentage of sexually mature in- 

 dividuals appears to be correlated with the length of the period during which whales 

 have been hunted in a locality". 



The same author (loc. cit., p. 108), after discussing the evidence of movements of 

 immature and mature whales, fat and lean whales and whales covered with diatom film 

 and scars, draws the conclusion that " The various maxima noticed in the season-graphs 

 are thus not necessarily due to the continued migration of a simple stock of whales. 

 There is good reason for believing that they are, or may be, the resultant of a com- 

 plex series of movements, partly of whales, often immature, from the north, and 

 partly of well fed individuals moving northwards from their Antarctic feeding 

 grounds". 



Now the arrival of batches of whales at different stages of maturity has already been 

 touched upon (p. 355), and a sequence of physically mature, sexually mature not 

 physically mature, and immature in December, January and February has been demon- 

 strated. This sequence may be simply an expression of the different rates of progress 

 physically possible to the different sections of the community ; for physically mature 

 whales are, on the average, one metre longer than the rest of the sexually mature whales 1 

 and the latter are, of course, considerably longer than the immature. These differences 

 coming into play on a long migration would be an efficient cause of segregation. There 

 is, however, no evidence concerning this migration other than that already indicated by 

 the heavily scarred condition of the larger whales. Against this there is the undoubted 

 fact that batches of whales appear in the South Georgia catches covered with thick 

 diatom film (Bennett, 1920), which suggests strongly a stay of some length in Antarctic 

 waters. 



There is evidence that in the early part of the season, when the influx would be 



1 The average length of 329 female Finners with less than fifteen corpora lutea is 21-41 m.; that of the 

 remaining 143 mature whales is 22-41 m. 



