NOTES ON THE SPECIES 259 



While the observation of the difference in colour of similarly preserved samples of 

 skin film and pelagic forms indicates some difference in composition of the endochrome, 

 it is difficult to avoid the conclusion that it is rare for C. ceticola to be actively parasitic. 

 The epidermis beneath the film appeared healthy on a large majority of the whales 

 examined. Probably nutrition is partly holophytic, partly saprophytic by utilization of 

 epidermal cells which have died naturally. In rare cases diatoms have been observed to 

 penetrate the epidermis as indicated in Plate XI, fig. 4, when there is no doubt that 

 their presence leads to its rapid disintegration. In all such instances they appear to gain 

 access to the subcutaneous layers through old scar tissue. 



A curious feature sometimes observed in fresh samples was the presence of numerous 

 transparent protoplasmic strands, reminiscent of the tangle roots of a bulbous plant, 

 apparently issuing from pores in the superior valves. An attempt has been made to 

 depict these in Plate XI, fig. 2. A similar phenomenon is known to occur in several 

 free-living forms, but it appears probable that these processes may furnish the means 

 by which nutriment can be absorbed saprophytically or even parasitically. In all cases 

 where actual penetration of the epidermis by C. ceticola has been observed the diatoms 

 appeared to be fixed to the tissues by their sucker-like inferior valves, while the superior 

 valves with their armature of protoplasmic processes project into the lacunae so formed. 



Cocconeis imperatrix, A. Sch. Judgingfromtheremarksof Peragallo(i92i, pp. 51, 52) 

 it seems probable that the C. kerguelensis of Petit (1889, p. 116, pi. x, fig. 5) and the 

 C. costata var. kerguelensis of Schmidt should be regarded as varieties of this species. 

 Petit's observations also make it seem probable that the C. scutelliim var. ampliata of 

 Grunow should be included in the synonymy. The considerable range of variation ex- 

 hibited by C. imperatrix is well illustrated by the figures given in Schmidt's Atlas (1890- 

 1902, Taf. 189, figs. 10-15). This variation, especially in size, was noticeable in the 

 littoral forms found at South Georgia, but the individuals found upon whales were 

 very uniform in size, averaging 61 x 55^ and corresponding closely to Schmidt's 

 fig. 15, but with twenty-six pairs of costae. The colour of the endochrome also differed 

 from that of the kelp dwellers, which was yellowish brown, the individuals found upon 

 whales having pale greenish cell contents. The littoral forms showed no trace of micro- 

 spore formation, but those observed in the skin film frequently contained dark spherical 

 highly refractive bodies thought to be microspores. 



Cocconeis gautieri, H.v.H. This is another variable species first recorded by van 

 Heurck (1909, pp. 17, 18, pi. ii, figs. 30, 31 and 33) from a bottom sample obtained in 

 64° S Peragallo (1921, pp. 52, 53) is of the opinion that it should probably be regarded 

 as synonymous with C. schuettii, H.v.H., first recorded in the same bottom sample. 

 C. gautieri was not observed at South Georgia except upon whales, and the frustules 

 were always smaller than the type, averaging 49 x 38^1. Peragallo found it to be a 

 common littoral form at the Palmer Archipelago and farther south. 



Cocconeis wheeleri, n.sp. This form was first discovered by Dr J. F. G. Wheeler 

 upon a Humpback whale taken at South Georgia during the 1929-30 season, and was 

 observed twice during the following season, in each case upon Humpbacks. It has 



