TERMINOLOGY: PREVIOUS WORK 269 



the year, so that one would need to speak of an ' early summer ' or ' summer increase ' 

 in describing the phenomenon in terms of the seasons. As it is obviously completely 

 analogous to the spring increase of the northern hemisphere, I have endeavoured to 

 avoid all possibility of confusion by the use of the expression 'main phytoplankton 

 increase'. The secondary (and usually much lesser) autumnal increase is common to 

 both hemispheres also, but has a corresponding time distribution in both, so that no 

 alteration in terminology is needed. The reversal of the seasons in the southern hemi- 

 sphere is represented by starting all time scales on i July, so that i January is to be 

 regarded as midsummer or ' mid-season '. 



Owing to the peculiar conditions found within the Antarctic zone, the terms 

 'oceanic', 'neritic', 'holoplanktonic', etc. are difficult to apply with the precision 

 originally intended by Haeckel (1890), and it has been found necessary to adopt a 

 special grouping system for the ecological characterization of the important species. 

 This is described in detail on pp. 281-5. It will be seen that while a binary system, 

 similar to the classical one evolved by Gran (1902) for the northern hemisphere, could 

 not be applied, his concepts have been followed as closely as possible. The system 

 proposed by Hendey (1937, pp. 226-7) is not very helpful, for he did not attempt to 

 take into consideration the differences in hydrological conditions within the Antarctic 

 zone. With regard to individual species many of his descriptions prove sound, but there 

 are important exceptions due to the limited amount of material he examined. This was 

 doubtless ample for taxonomic purposes, but inadequate for ecological description. A 

 few of my own earlier conclusions (Hart, 1934, pp. 153-74) ^^e subject to the same 

 criticism now that more extensive observations have been obtained. Hendey's taxono- 

 mic work, on the other hand, is of the highest value, and I have endeavoured to bring all 

 our results into line with his revised classification of the Bacillariophyceae. 



PREVIOUS WORK 

 Before the Discovery investigations were begun, our knowledge of the Antarctic 

 phytoplankton was derived from accounts of the material brought back by various 

 expeditions which had geographical exploration as their main object, or were engaged 

 upon large-scale oceanographical programmes of which the more southerly cruises 

 formed but a small part. These were: the voyage of H.M.S. 'Challenger', 1873-6 

 (Castracane, 1886), the 'Belgica' Expedition, 1897-9 (Van Heurck, 1909), the German 

 Deep Sea Expedition, 1898-9 (Karsten, 1905-7), the German South Polar Expedition, 

 1901-3 (Heiden and Kolbe, 1928), the Scottish National Antarctic Expedition, 1902-4 

 (Mangin, 1922) and the second French Antarctic Expedition, 1908-10 (Mangin, 1915). 

 All these accounts are mainly concerned with systematic descriptions of the organisms 

 obtained, though Mangin made a noteworthy attempt to determine the relative im- 

 portance of the various species, and Karsten's included several observations of general 

 biological interest, including numerous abstracts from Schimper's field-notes. More 

 recent and very much more extensive observations have only served to show that this 

 body of work provides ample foundation for our knowledge of the systematics of the 



