28o DISCOVERY REPORTS 



true "constituent species", i.e. present during the life of the whale. The reasons for 

 regarding these as true constituents of the skin film are discussed at length ; the species 

 are: Lycmophora lyngbyei, Ktz., Cocconeis gaiitieri, H.v.H., C. imperatrix, A. Sch., 

 Naviciila spp. and Gyrosigma {Rhoicosigmd) arcticum, Cleve. 



The formation of microspores in Cocconeis ceticola is described, and it is shown that 

 spore formation is commonest at the beginning and end of the season. As it seems 

 certain that diatom film is only formed upon whales in Antarctic waters, it is thought 

 that these spores furnish the chief means of dispersal of the species. The small nucleus 

 of whales known to remain in the far south during the winter would serve to maintain 

 survival, and the shedding of vast quantities of microspores into the sea in the 

 following spring, when the schools congregate on the feeding grounds, apparently leads 

 to rapid reinfection of the new arrivals. Spore formation was at a minimum in January, 

 but showed a great increase in February and March. Examination of Sei whales, which 

 only come south late in summer, suggests that a period of about one month elapses 

 between the arrival of whales within the Antarctic Zone and the formation of visible 

 diatom film upon them. The great increase in spore formation at the end of the season 

 will obviously tend to ensure that a majority of the whales that remain south through 

 the winter become infected. 



Systematic and general notes on all the species thought to be true constituents of 

 the skin film have been given. The presence of numerous protoplasmic processes 

 issuing from pores in the frustules of the principal species Cocconeis ceticola has 

 been observed, and there are indications that it may rarely be actively parasitic upon 

 the whales, penetrating the epidermis via old scar tissue. It is thought, however, that 

 its normal mode of nutrition is holophytic, perhaps partially saprophytic upon epi- 

 dermal cells which would have died naturally, whether the diatoms were present or 

 not. Naviciila sp. ? was also observed to have penetrated the epidermis upon two occa- 

 sions, with a markedly deleterious effect upon it. 



A brief outline of existing knowledge of whale movements, with special reference 

 to South Georgia, is then given. Southern Sei whales are known to make only a brief 

 journey southwards towards the end of the whaling season, and the period of their 

 maximum abundance round South Georgia falls in March. The general nature of the 

 migration of the larger rorquals, southwards in summer to feed and northwards in 

 winter to breed, has long been a matter of common knowledge, but further details re- 

 main practically unknown. There is some evidence that on the South Georgian grounds 

 the general trend of movement is easterly. Blue whales show a strong southerly com- 

 ponent in addition, which agrees with the observation, now well established, that the 

 centre of concentration of Blue whales lies well to the south of that of Fin whales. There 

 is a definite southward movement of the concentration centre of both species as the 

 season advances. In some seasons the return movement towards warmer waters is well 

 marked in the later months. The Blue whales commonly illustrate this movement more 

 clearly than the Fin whales. The smaller whales, mostly immature, tend to lag behind 

 on the southern migration and arrive in large schools, often segregated according to sex, 



