THE SEASONAL VARIATION WITH THICK FILM 



275 



south during December, and since all the figures are high they support the view that the 

 whales were concentrated to an unusual degree at the beginning of that season. 



The fact that Fin whales are more frequently infected than Blue whales on the South 

 Georgian grounds, is amply borne out by these figures. While the number of whales 

 examined was not large enough to be conclusive, however, the collection made by 

 Mr Laurie in the ' Southern Princess ' indicates that Blue whales are just as frequently 

 infected farther south. Evidently the maximum of diatom infection is to be found at 



OCT 



40H 

 30 

 20 H 

 10 



NOV 



FEB MAR&APR 



1929-30 



~/0 



4-0 

 30- 

 20- 

 10- 



1930- 



NOV 



DEC 



JAN FEB* MAR 



Fig. 6. The seasonal variation in the percentage of whales with thick film during the three 

 seasons studied at South Georgia. Solid lines Fin whales, pecked lines Blue whales. 



the maximum southern concentration of the given species of whale, and here we have 

 but another expression of the fact that the centre of the southern concentration of Blue 

 whales lies well to the southward of that of the Fin. The opinion that most of the Blue 

 whales taken on the South Georgian grounds during the seasons studied, were on passage 

 to and from other feeding grounds also gathers strength from these figures. 



It will be seen from the small number of observations obtained at the South Shetlands 

 at mid-season (p. 271) that the percentage of Fin whales with thick film was exceptionally 

 high, while the percentage infection was quite normal. It follows that at the time the 



