126 DISCOVERY REPORTS 



thickness expressed as a percentage of body length is plotted by months, immature 

 males under 12 m. long being plotted separately from the mature ones over 12 m. long. 

 Immature whales were only found at South Africa and are very noticeably fatter than 

 adults. They thus resemble the immature balaenopterid whales, especially the Hump- 

 back and to a lesser degree the Sei, Fin and Blue whales. Both immature and adult 

 whales at South Africa show a decline in fatness towards the end of the southern 

 summer, and mature whales as well as immature ones are above the average fatness 

 (indicated by the horizontal line in Fig. 34) at the beginning of the season. In male 

 Sperm whales, at South Georgia, indications are shown of a rise in fatness until the 

 middle of the season, followed by a drop towards the end. 



The fatness of female Sperm whales is shown graphically by months in Fig. 35, which 

 relates only to South African whales. The average fatness is greater than in males: preg- 

 nant whales tend to be fatter and lactating ones thinner than the average, and resting 

 whales are intermediate. There is not, however, the marked fatness in pregnant whales 

 and leanness in lactating ones that is found in the balaenopterid whales. 



PARASITES 



EXTERNAL 



The commonest external parasite of the Sperm whale is the amphipod Cyamiis. It was 

 present in twenty-two out of the thirty-eight whales regarding which notes on the 

 external parasites are available. It was usually present in greatest numbers in the 

 umbilical and genital regions, and occurred scattered over the rest of the body in smaller 

 numbers. The open pits in the blubber, referred to below, were also a favourite position 

 for Cyamiis. 



Penella was only recorded once from this species, a male at Durban carrying two very 

 small Penella, one on the flank and one on the head. 



One large male Sperm whale at South Georgia was infested with Coronula of small 

 size. The barnacles, up to 2 cm. in diameter, were scattered irregularly all over the body. 

 Stalked barnacles of an undetermined species were found on the lower jaw of one male 

 at South Georgia. 



A pathological condition of the skin of the head was observed in two male whales at 

 South Georgia and was noted as " ? fungoid growth". 



Diatom films were frequently present on the skin of male Sperm whales at South 

 Georgia, but were not observed on the whales at South Africa. Of the twenty-three 

 whales examined for diatom film, nineteen carried patches of greater or lesser extent. 

 The film usually occurred as patches on the head, less frequently on the flanks, flukes 

 and back. Cocconeis ceticola appeared to be the dominant species, but two species of 

 Naviciila, and Nitzschia closterium were also recorded. The presence of diatom film 

 proves that the whales carrying it have been at least a month in the Antarctic Zone, 

 as shown by Hart (1935). 



Sperm whales, like the Whalebone whales, while in temperate and tropical waters 

 are subject to attack by some unknown agent which removes semi-ovoid pieces of blubber 



