PREVIOUS WORK: DISCOVERY INVESTIGATIONS 275 



subsequently to that available to Hendey, and that limitations of material in my own 

 earlier work have led me into some similar errors. 



Nitzschia seriata should not, I believe, be regarded as neritic only ; many observations 

 of this widespread species from all parts of the ocean in considerable abundance were 

 already available. 



Corethron criophilum should surely be included among the species typical of Brans- 

 field Strait, where I had already shown it to be a dominant (over 90% of the (net) 

 plankton throughout the year; Hart, 1934, p. 159). 



The omission of Thalassiothrix antarctica from the table of typical forms is un- 

 fortunate, for it is often one of the most important of the larger species in the northern 

 part of the Antarctic zone, and, more rarely, farther south (Hart, 1934, p. 40; Hardy in 

 Hardy and Gunther, 1935, p. 66). 



The two most important southern species of Thalassiosira — Th. antarctica and Th. 

 subtilis — are tabulated by Hendey as oceanic, holoplanktonic. We should now regard 

 them as definitely neritic (and ice-edge), as seems true for most members of the genus 

 throughout the world. The probability that they are meroplanktonic is strong. My own 

 earlier remarks on Th. antarctica ('widely distributed...'. Hart, 1934, p. 157) were 

 intended to apply to a.more restricted area, but may have led Hendey astray here. A 

 similar remark of mine concerning Biddulphia striata (p. 165) may also have been mis- 

 leading. Hendey tabulates it as holoplanktonic, oceanic and neritic. We should now 

 regard it as meroplanktonic and very definitely neritic, being rare even along the ice- 

 edge in the open ocean which some neritic species seem to find an adequate substitute 

 for a coast. Such mistakes as these are due entirely to the localization of most of our 

 earlier work in the complicated Falkland sector. Until even longer oceanographical 

 cruises were undertaken, it was impossible for us to realize how the vast scale of 

 biophysical relationships in the southern ocean leads to neritic influences being felt at 

 much greater distances from land than in the better known waters of the northern 

 hemisphere. 



Chaetoceros atlanticum is omitted from Hendey's table and is said in his notes to be 

 unimportant far south. It is quite true that it is rare in the extreme south, but in the 

 more northerly parts of the Antarctic zone it is one of the most numerous medium-sized 

 chaetocerids, and, since his 'cold-water flora' apparently includes most of the sub- 

 Antarctic zone as well, it should certainly be included in any table of typical forms. 



There are minor points concerning less important species of Chaetoceros on which we 

 differ. Thus Hendey tabulated Ch. castracanei, Ch. chiinii and Ch. schimperianum as 

 neritic while we now tend to regard them as oceanic. The evidence is not yet conclusive, 

 particularly with regard to the last named. 



Finally, Hendey has tabulated all the Actinocyclus spp. he examined as neritic, no 

 doubt correctly, but has not considered the smaller members of the genus we have 

 found in our more recent work to be very constant constituents of the oceanic plankton. 

 Though never occurring in great numbers, these are important and certainly ' typical ' 

 in winter. 



