252 d;iscovery reports 



Delafield's haematoxylin. The diatoms, epidermal and dermal cells take up this stain 

 in very different amounts, so that a good distinction was readily obtained. 



The numerical data relating to the whales examined at South Georgia have not been 

 treated statistically, as the numbers in the month groups are scarcely large enough to 

 justify such a procedure. The season's catches have been divided into month groups, 

 and at the end of the season, when whales were getting scarce, the last two months have 

 usually been treated together. This does not lead to so much distortion as might be 

 expected, for whaling rarely continued beyond the second week in April, and in the 

 exceptionally poor 1 930-1 season, when the February and March figures were run 

 together, only ten whales were captured during the latter month. In studying the 

 seasonal variation in diatom infection and correlation with fatness, arithmetical per- 

 centages and means have been employed. The fatness of a whale has been taken as the 

 blubber thickness on the flank, at the level of the dorsal fin, expressed as a percentage 

 of the length of the whale, measured from the tip of the snout to the notch of the flukes. 

 Thus a whale 23-68 m. long with blubber 10 cm. thick is said to have a fatness of 

 0-42. This method is that employed by Mackintosh and Wheeler (1929, p. 365). I am 

 indebted to my wife for help in the preparation of the numerical data. 



When this work was begun Dr J. F. G. Wheeler, who was in charge of the Marine 

 Biological Station in 1930, gave me the benefit of his experienced advice; he was the 

 discoverer of a new type of film-forming diatom, which has been named in his honour. 

 Thanks are due to Dr F. D. Ommanney, who first observed diatoms actually penetrating 

 the epidermis of whales, for bringing this fact to my notice, and kindly lending me slides 

 and a photograph illustrating the phenomenon. I am greatly indebted to Mr F. W. Mills 

 and Mr E. J. Steer, for systematic references, and to Mr A. Saunders for section cutting 

 and preparing the drawings reproduced in Plate XL Finally I would like to 

 acknowledge most gratefully the help received from the authorities in charge of the 

 general and cryptogamic sections in the library of the British Museum (Natural History). 



THE DISPOSITION OF THE FILM 



The film is commonest upon Blue and Fin whales, Balaeiioptera musctilus and 

 B. physaliis. It is also known to occur more rarely upon the Sei whale, B. borealis, the 

 Humpback, Megaptera tiodosa, and the Sperm whale, Physeter catodon. The Sei whale 

 only makes its appearance in Antarctic waters late in the season, so that the reason for 

 the scarcity of film on the specimens examined is obvious. It will be shown subse- 

 quently that in all probability quite a large proportion of the Sei whales ultimately be- 

 come infected, but by that time the whaling season has generally finished. The whalers 

 have a saying " when the Sei whale come, we go " ; moreover, Sei whales are never taken 

 when larger and more profitable species are available. 



The Sperm whales taken in the far south are all old lone bulls (cf. Hamilton, 1914, 

 p. 22), and these again are rarely captured when other species are available, as their oil 

 cannot be mixed with that of other whales and their subsequent treatment therefore 

 entails much extra labour. 



