254 DISCOVERY REPORTS 



recorded as littoral, bottom or ice-forms in Antarctic or sub-Antarctic waters. It is 

 thought, however, for reasons shortly to be discussed, that some of them are definite 

 constituents of the skin film while the whales are alive. Thus the list of diatoms recorded 

 on the skins of whales may be made out as follows : 



True constituents of the skin film Fortuitous species 



Lycmophora lyngbyei, Kiitzing Coscinodiscus spiralis, Karsten 



Cocconeis ceticola. Nelson Fragilaria antarctica, Castracane 



C. imperatrix, A. Schmidt F. striatula, Lyngbye 



C. gantieri, H. van Heurck Navicula grunowi, Rabenhorst 



C. wheeleri, n.sp. Nitzschia closterium, Ehrenberg 



Navicula sp.? 



Navicula spp. 



Gyrosigma (Rhoicosigma) arcticum, Cleve 



As already stated, the small indeterminate species of Navicula and Cocconeis wheeleri 

 have been observed to form film without C. ceticola, but with regard to the other species 

 thought to be true constituents of the skin film the facts are not so conclusive. All are 

 known as littoral or bottom forms, and most have been observed upon southern sea-ice. 

 They are not very common upon whales, and it might well be argued that their presence 

 is accidental, and that they become attached after the whale's death. Against this view 

 it may be cited that the whales are towed in tail first, which would be expected to wash 

 off the cutaneous investment rather than add to it. Further, the time elapsing between 

 capture and flensing, which was known approximately for over forty whales upon which 

 " other species " were recorded, did not bear any relation to the numbers of these other 

 species present. Taking them individually: 



Lycmophora lyngbyei is a very common littoral form growing luxuriantly upon kelp 

 in the Magellan region and at South Georgia, and in the northern hemisphere. Of all 

 littoral forms the tychopelagic habit is perhaps most strongly marked in members of 

 this genus. For this reason alone their presence upon whales would have been regarded 

 as accidental but for the following considerations : they are known to have a remarkable 

 capacity for attaching themselves to objects at a considerable distance from land, and 

 forming colonies in a comparatively short space of time. They have been observed 

 living epizootically on the legs of Copepoda and Mysidacea. Gran (1912, p. 337) gives 

 an instance of the way in which attached forms of littoral diatoms develop on objects in 

 the open sea far from land. Finally, thick growths of Lycmophora lyngbyei are common 

 upon the Coronnla shells at South Georgia, and have been observed to spread on to the 

 surrounding epidermis. Evidently the body of a whale does not form an ideal sub- 

 stratum for this species, but equally evidently it may occur amongst the film of Cocconeis 

 ceticola upon living whales. 



C. imperatrix and C. gaiitieri have both been observed in the skin film, the former 

 abundantly, the latter rarely. Both are known as littoral and bottom forms in Antarctic 

 waters, and C. imperatrix from the Magellan region also. The latter is exceedingly 

 abundant on the kelp round South Georgia and is stated by Earland (1933, p. 30) to be 



